7 Microsoft Teams Phone Problems and How to Fix Each

1. Calls go straight to voicemail

Usual cause: call answering rules or presence, not a system fault. If the user's status is Do Not Disturb, or their unanswered-call setting sends calls to voicemail immediately rather than after ringing, inbound calls never ring at all.

Fix: check Settings, then Calls on the user's Teams client before escalating anything. Also check whether a call queue's presence-based routing is skipping them because their status says unavailable. If they're in a queue, confirm they haven't opted out and forgotten.

2. The desk phone rings but the app doesn't, or vice versa

Usual cause: the user is signed into one and not the other, or simultaneous ring is configured in a way nobody remembers setting.

Fix: verify the same account is signed in on both devices, then check the user's call forwarding and simultaneous ring settings. A user who once set "ring my mobile also" and forgot is a common culprit.

3. One-way audio

Usual cause: network, almost always. Firewall rules blocking media traffic in one direction, or a router interfering with the connection.

Fix: confirm the required Microsoft 365 network endpoints are permitted through your firewall. This is a firewall conversation rather than a Teams one, and it usually needs whoever manages your network rather than whoever manages Teams.

4. Choppy or robotic audio

Usual cause: bandwidth contention or Wi-Fi. Voice packets are small but intolerant of jitter and loss.

Fix: wire desk phones rather than relying on Wi-Fi, prioritize voice traffic on the router, and check real upload capacity rather than advertised speed. The causes are the same as any VoIP system — see the six real causes of bad call quality.

Teams' own Call Quality Dashboard is genuinely good for diagnosing these. It'll show you jitter, packet loss and which network path the call took, often pinpointing a single site or a single access point.

5. External calls fail but internal calls work

Usual cause: PSTN connectivity or licensing. Teams Phone without a calling plan or operator connection can't reach the outside world, and internal Teams-to-Teams calls don't touch the PSTN at all — which is why they keep working and mask the problem.

Fix: verify the user has Teams Phone licensing and a PSTN path. See licensing explained. If international calls specifically are failing, check whether prepaid calling credit is configured and funded.

6. Caller ID shows the wrong number

Usual cause: caller ID policy, or agents calling out from a queue without the queue's identity applied — so customers see and call back an individual's direct line instead of the main number.

Fix: caller ID policies in the admin center control what external parties see. For queues, this needs setting deliberately; it isn't automatic.

7. A queue or auto attendant stopped answering

Usual cause: the resource account lost its license, or its number assignment changed during some other piece of work.

Fix: check the resource account first, every time. It's the single most common point of failure in a Teams voice deployment, and it fails silently — nothing alerts you, callers just stop getting through.

The diagnostic order that saves time

When something isn't working, check in this sequence. It resolves most issues before you reach step four:

1. Licensing. Does the user or resource account have what it needs, and is it actually assigned?
2. User settings. Presence, call answering rules, forwarding, queue opt-out.
3. Configuration. Queue and attendant routing, caller ID policy, emergency addresses.
4. Network. Firewall, bandwidth, Wi-Fi, QoS.
5. Microsoft service health. Occasionally it genuinely is them.

Most teams start at step four because network problems feel like the likely culprit. In practice, the first two account for the majority of tickets.

What to gather before calling for help

If you do escalate, having these ready shortens things considerably: the affected user's UPN, the exact time of a failing call, the number dialed, whether it fails every time or intermittently, and whether it affects one user or several. A single failing call with a timestamp is worth more than a general description.

When it's none of these

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