Your 0800 went down and nobody told you: how to monitor 0800 and IVR

How does an 0800 stay down all night without anyone noticing?

An 0800 stays down all night with no alarm when the failure happens before the call reaches your equipment. The PBX receives nothing, so it has nothing to complain about; the SIP trunk stays registered; and in the small hours, few calls is normal. Only the callers notice, and callers give up.

One night, hour by hour

The timeline below is an illustration, built to show the mechanism, not a real case. The times and the cause are hypothetical; the pattern is what matters.

Time	What happens	What the dashboards show	What the caller hears
01:50	A change at the carrier breaks the 0800’s route to your trunk	All green	Nothing yet
02:00	First call after the change	No calls on the PBX; SIP trunk registered	Silence, then the call drops
02:00 to 07:59	Customers try and give up	Low volume, normal for the small hours	Silence
08:00	Live-agent support opens	Empty queues, idle agents	Silence
09:00	A supervisor finds the empty queue odd and calls from their own mobile	Nothing has changed	The supervisor hears silence
09:30	A ticket is opened with the carrier, with no start time and no error code	Nothing has changed	Silence

The customer who called at 2:00 a.m. left no trace on any of the company’s equipment. The outage started at 01:50 and was noticed at 09:00: 7 hours and 10 minutes. And the ticket opened at 9:30 starts weak, because nobody can say when the failure began or what the route was responding.

On the same night, with a test call every 15 minutes at Monitor’s default pace, the 02:00 test would fail, so would the retries at 02:02, 02:04 and 02:06, and at 02:06 an incident would open with the SIP code of every call, alerting the first tier of the escalation ladder by email and SMS. The difference is 6 hours and 54 minutes, from 02:06 to 09:00.

Why the dashboards stayed green

Each dashboard was answering a different question from the one that mattered:

• the PBX said it was up, and it was; it has no way of knowing about calls the carrier stopped delivering;
• the SIP trunk showed as registered, and it was; registration tells the carrier where to deliver calls, but the 0800 translation happens at another point in its network;
• the volume chart showed few calls, which is normal in the small hours.

None of these measurements is wrong. They just don’t call the 0800. The voice circuit monitoring guide compares what each method can see.

Why does an 0800 stop connecting?

An 0800 stops connecting because of failures anywhere between the caller and whoever answers: the carrier’s route, number portability, the IVR platform, the SIP trunk behind it or the message itself, swapped without notice. Almost all of these points sit outside your PBX and raise no alarm on it.

The carrier’s route

An 0800 is not a geographic number. It is free for the caller, as Anatel Resolution 749/2022 sets out in art. 18, and the carrier translates it into a destination: your trunk, a DID or the platform that hosts the IVR. That translation is a setting in the carrier’s network. A botched destination change, a mistake during maintenance or an interconnection problem between networks breaks the route without anything changing on your side.

The route can also vary with the origin. A mobile call and a landline call, or calls from different carriers, can take different paths to the same 0800, and a failure can affect only one of them. The guide why an 0800 won’t connect from a mobile phone covers that case.

Number portability

When the 0800 or the destination number moves to another carrier, every network has to start routing calls to the new one. Until that happens everywhere, the number works from some origins and fails from others. It is a partial, treacherous failure: whoever tests from their own phone may be on an origin that has already been updated, and conclude that everything is fine.

The IVR platform

The IVR can run on the PBX, on a contact center platform or in the cloud. When that platform goes down, runs out of channels or gets a flow published with an error, the call rings with nobody answering, is rejected, or answers and drops. If the platform belongs to a third party, your PBX takes no part in the call and does not see the failure.

The SIP trunk behind the 0800

Behind the IVR or the 0800’s destination there is a SIP trunk, and it has its own failure points: exhausted channels, which usually show up as SIP 503 with Q.850 cause 34 (no circuit/channel available); a lost SIP registration; a faulty SBC; or NAT and a SIP ALG that let the signaling through and block the audio, which produces a silent call. The guide silent calls and one-way audio covers that last case in detail.

The greeting swapped without notice

A new version of the IVR flow, a holiday recording left switched on, a forgotten test message, or a route change that sends the 0800 to another customer’s IVR on the platform. The call connects and, as far as the signaling is concerned, everything worked. The caller, however, hears the wrong message, and for them the 0800 is down.

Early media: a recorded message instead of ringing

Before answering, a route can send audio: this is early media, described in RFC 3960, which usually arrives with the 183 Session Progress response. It is meant for playing the ringback tone, but it is also used for carrier announcements such as “this number does not exist” or “this number is temporarily unavailable”.

To the caller, it feels like a call that went somewhere: a voice was heard. But your company never answered, and your PBX never saw the call. Monitoring that only checks whether there was audio would pass this test. That is why testing an 0800 has to compare what was heard with the expected greeting, not just detect sound.

How do I test the 0800 and the IVR from outside?

Test the 0800 from outside by calling the way a customer calls: from another carrier, from a mobile phone and a landline, and at the hours when nobody on the team is watching. For the IVR, check that the greeting that answers is the expected one. A test placed from inside your own network does not go through the carrier’s route and cannot see the carrier’s failure.

The manual test

A good manual test always follows the same steps, so the result can serve as evidence:

1. Call from at least two origins: a mobile phone and a landline, ideally on carriers other than the one that serves the 0800.
2. Write down the time to the second and the calling number of each attempt.
3. Listen to what happens before the answer: silence, ringback, a busy signal or a carrier announcement.
4. Check the greeting: is it your company’s, the current version, with the right first menu?
5. Test the IVR menu: press an option from the first menu and see whether the IVR recognizes the tone. DTMF usually travels inside RTP, as RFC 4733 describes, and a negotiation failure makes the IVR ignore the keys even while voice gets through.
6. Repeat outside business hours at least once, because the IVR may switch to a different flow at night.

The manual test has an obvious limit: nobody calls at 3:00 a.m. on a Sunday, every 15 minutes. It is for investigating and for checking after a change, not for keeping watch.

The automated test

The automated test is a scheduled test call, placed from a platform outside your network, that calls the number and judges the result on its own. In Monitor, calls go out from the 2N5 platform to support numbers, 0800, 0300, 4004 and landline numbers, and each number has its own schedule, at intervals or at fixed times, including nights and weekends.

During setup, 2N5 records each number’s reference greeting. Every test call compares what it heard with that recording: a different message, such as a carrier saying the number does not exist, does not pass. For an IVR, busy, no answer or ringing until timeout also counts as a failure, because it should answer every call on its own. The same comparison measures voice quality, MOS-LQO, a score from 1 to 5 in the terminology of ITU-T P.800.1.

Two rules protect people. The audio of a test call is kept only when what answers is the recording or the IVR on file, encrypted and deleted after 90 days; a person’s voice is never kept. And if the circuit could be answered by a person, they hear a message saying it is an automated test, and the call ends.

On cost: the test calls are part of the service. For an 0800, as for any inbound call, the termination rate follows your contract with the carrier. See 0800 and IVR monitoring.

What a test call does not see

A call that hears the greeting and hangs up does not navigate the menu. It does not check whether each option leads to the right queue, whether DTMF is recognized or whether live agents are available at that hour. Those points need the manual test after every flow change.

And a test that always starts from the same origin cannot see a failure that applies only to another one, such as an 0800 that won’t connect from a mobile phone on a particular carrier. The automated test watches the whole path, around the clock; the manual test from other origins completes the picture.

What do the SAC decree and Anatel require of an 0800?

Decree 11,034/2022 (Decreto nº 11.034/2022) requires the SAC, the customer-service channel Brazilian law regulates, to be reachable 24 hours a day, 7 days a week, and makes phone support mandatory. For telecom providers, Anatel’s RGC requires free phone support available 24 hours a day. Measuring the 0800’s availability is how you show those rules were met.

Rule	What it requires
Decree 11,034/2022, art. 4	SAC access 24 hours a day, 7 days a week, through at least one channel
Decree 11,034/2022, art. 4, § 2	Phone support is mandatory
Decree 11,034/2022, art. 5, I	At least 8 hours a day of live-agent phone support
Decree 11,034/2022, art. 5, II	Complaint and cancellation options in the first menu
Decree 11,034/2022, art. 12, § 3	Call recordings kept for at least 90 days
Anatel, RGC (Res. 765/2023), art. 15	Free phone support available 24 hours a day; a live agent 24 hours for urgent requests and from 6:00 a.m. to 10:00 p.m. for everything else
Anatel, RGC (Res. 765/2023), art. 18	First menu with automatic cancellation, complaints and live-agent support
Anatel, Res. 749/2022, art. 18	0800 free for the caller; 0300 and 0303 with shared cost

The decree has applied to SACs in regulated sectors since October 3, 2022. The RGC has applied to telecom providers since September 1, 2025.

The rules say what has to be available; showing that it was is the job of whoever runs the 0800. A test call every 15 minutes, with each result kept, is an hour-by-hour record that the number connected and the IVR answered with the expected greeting. Monitor’s SLA reports show each number’s availability over the year and the month, with every failure and the moment someone took ownership. The content of the first menu, for its part, is checked by whoever listens to the IVR after each change.

What does the caller hear on each 0800 failure, and what does the test record?

Each 0800 failure sounds different to the caller and leaves a different trace on a real test call. The table below links the likely cause, what the customer hears and what the test records, so that your first message to the carrier already says where to look.

Failure	What the caller hears	What a real test call records
The carrier cannot find the 0800’s destination	Silence and a drop, or the number-does-not-exist announcement	SIP 404, or early media with the carrier’s announcement, which does not match the reference
The route rejects the call	Silence, an error tone or an announcement	SIP 403 or SIP 603, with the Q.850 cause when one is sent
The trunk behind the 0800 has no channels	A busy signal or a congestion announcement	SIP 503, for example with Q.850 cause 34
The IVR platform is down	Rings without answering, or drops	SIP 480 or SIP 408; ringing until timeout is a failure for an IVR
The IVR is busy	A busy signal	SIP 486: a failure for an IVR
Incompatible codecs on the route	The call does not connect	SIP 488
The greeting swapped without notice	A different message: a holiday one, an old one or another company’s	Call answered, but the greeting does not match the reference recording: failure
Silent call	It answers and stays silent	Call answered without the expected greeting: failure
One-way audio	The caller hears but is not heard	On a circuit with a test tone or echo, the tones sent do not come back: failure
Choppy voice	The greeting with gaps and noise	MOS-LQO below 3.0: the call counts as degraded
The IVR does not recognize the keys	The IVR repeats the menu or says the option is invalid	Does not show up on a call that only listens to the greeting: needs the manual test

Two readings apply to every row. An 0800 that rings without answering and a route that cancels the call both look like no answer to the tester, sometimes with SIP 487 when the test itself gave up waiting; a SIP 180 followed by nothing is not a success. And the same SIP response can come with different Q.850 causes, which the carrier uses to find the point in its network. The list of Q.850 causes and the SIP code lookup help read each one.

What should I do when the 0800 goes down?

When the 0800 goes down, confirm the failure from another origin, find out whether calls are reaching your equipment, gather the evidence and open the ticket with the carrier using it. While the carrier works on it, tell the support team and reinforce the other SAC channels. Afterwards, record the start and end of the 0800 outage.

1. Confirm from outside. Call from a mobile phone and a landline, on different carriers. If one origin connects and another doesn’t, note which: that points to the route or to portability.
2. See whether calls reach you. On the SBC or the PBX, look for the INVITEs of the attempts at the time they were made. If none arrived, the failure is upstream of you, at the carrier or the IVR platform. If they arrived and were rejected, the failure is on your side.
3. Gather the evidence. The number called, the origins, the time of each attempt with seconds and time zone, the SIP code, the Q.850 cause when one is sent, the Call-ID and a recording of the message that played, if any did. Keep the last call that worked as well.
4. Open the ticket with everything in the first message. Ask for the ticket number and ask at what point on the route the call stops. A ticket with a time and an error code is harder to close with “no fault found”.
5. Protect customer service. Tell the SAC team and the supervisors, and reinforce the other support channels while the 0800 is down. If the carrier contract provides an alternate destination for the 0800, ask for the diversion.
6. Close with numbers. Record the start and end of the outage, because that is what goes into the month’s and the year’s SLA. The guide telephony SLA: yearly and monthly calculation shows the math. And ask why your team heard about it from a customer and not from an alert.

In Monitor, steps 1 and 3 happen on their own. Four failures in a row, by default (the first one and three retries), open an incident with a block ready to paste into the ticket: the circuit, the carrier, the first symptom, the SIP code and Q.850 cause of each call and the last healthy call. The escalation ladder alerts the first tier by email and SMS and climbs until someone takes ownership with one tap on the SMS link. When two good calls in a row confirm recovery, the incident closes and the customer’s contacts are notified. See alerts and escalation.

One caveat applies to any monitoring: if the problem is on the tester’s side, the test says nothing about the 0800. In Monitor, a test that could not run because of a problem on 2N5’s side is marked monitoring blind, does not count against the number, stays out of the SLA and does not wake your team.

How often should I test the 0800?

Test the 0800 as often as the availability target demands and at the hours when nobody is watching. With one call every 15 minutes and retries every 2 minutes, an overnight 0800 outage becomes an incident within 21 minutes; with one call an hour, a whole hour can pass before the first sign.

The worst-case math: an outage that starts right after a good test takes up to 15 minutes to be seen, plus 6 minutes for the three retries to confirm it, or 15 + 6 = 21 minutes to the incident. At the 15-minute pace, each number gets 24 × 4 = 96 test calls a day, each holding a channel for a few seconds, within a call limit that never competes with customers for a channel.

Three things help when choosing the schedule:

• Nights and weekends count more. That is when the 0800 is on its own. A 24-hour 0800 needs 24-hour testing.
• Fixed times complement the interval. A test at a set time, for example just before live-agent support opens, confirms the number at the moment the most customers are about to call.
• Each support number is a circuit. If the company has an 0800 for customers, a 4004 and a collections number, each has its own route and its own IVR, and each needs its own test. The voice circuit monitoring guide shows how to choose what to monitor.

The goal is simple to state: the next time the 0800 goes down at 2:00 a.m., the first person to know should be someone on your team, at 2:04 a.m., with the SIP code in hand, not a customer at 9:00 a.m.

Frequently asked questions

Why won't my 0800 connect?

The failure can be outside your PBX: the carrier stopped routing the 0800 to your destination, a number port was not updated on every network, the IVR platform went down or the SIP trunk behind it ran out of channels. The SIP code and Q.850 cause of a test call show where the call stopped.

How do I test an 0800 in the middle of the night without anyone having to call?

With scheduled test calls, placed from outside your network, that call the 0800 like a customer and check what answered. In Monitor, each number has its own schedule, at intervals or at fixed times, including nights and weekends, and each call compares the greeting it heard with the reference recording.

The 0800 connected, but it plays the carrier's announcement. Is it down?

For the caller, yes: the customer never reaches your company. That announcement usually arrives as early media, before any answer, or on a call answered by the carrier itself. Monitoring that only checks whether there was audio lets this through; you have to compare what was heard with the IVR's expected greeting.

What does the SAC decree require of an 0800?

Decree 11,034/2022 requires SAC access 24 hours a day, 7 days a week, through at least one channel, makes phone support mandatory, requires at least 8 hours a day of live-agent phone support and requires the complaint and cancellation options in the first menu. It has applied since October 3, 2022.

What should I do first when the 0800 goes down?

Confirm it from another origin, calling from a mobile phone and a landline on different carriers. Then check whether the calls reach your SBC or PBX: if none do, the failure is upstream of you. Gather the time, the SIP code, the Q.850 cause and the Call-ID of each attempt and open the ticket with the carrier using that evidence.

Sources

1. Decree No. 11,034/2022 (Decreto nº 11.034/2022): SAC rules, including 24-hour access and phone support
2. Anatel, Resolution No. 765/2023 (RGC), arts. 15 and 18: phone support and the first menu
3. Anatel, Resolution No. 749/2022, art. 18: 0800 free for the caller, 0300 and 0303 with shared cost
4. RFC 3261: SIP and its response codes
5. RFC 3960: early media, the audio before the answer
6. RFC 4733: DTMF carried in RTP
7. RFC 6432: Q.850 causes in the Reason header of SIP responses
8. ITU-T P.800.1: MOS terminology, including MOS-LQO

Keep reading

• Voice circuit monitoring: the complete guide
• 0800 and IVR monitoring
• Why an 0800 won't connect from a mobile phone
• Telephony SLA: yearly and monthly calculation
• Alerts and escalation
• SLA reports