Microsoft 365 Alert : Service Degradation – Microsoft Teams – Some users are unable to make Public Switched Telephone Network (PSTN) calls via Microsoft Teams – RESOLVED

10/11/2022 07:20:00 AM (GMT)

NHSmail Reference : INC32668299 

Microsoft Reference : TM455097

Issue Status : RESOLVED

Issue Description : Users are unable to make PSTN calls via the Microsoft Teams desktop and web clients.

More info : The issue predominantly effects Microsoft Teams PSTN calls made to extension numbers, though users may also be unable to make calls when selecting People Picker suggestions. To bypass this, users can leverage the dial pad to make calls directly without selecting suggestions. As another alternative method of making PSTN calls from the Microsoft Teams desktop client, users can also use the search bar and enter the command “/Call”. Further instructions on how to access and use the search bar can be found at,

Scope of impact : Your organization is affected by this event, and some users attempting to make PSTN calls via the Microsoft Teams desktop and web clients are impacted.

Final Update : 14/11/2022 15:35:00 PM – Microsoft has completed deploying the fix to the impacted environment and confirmed with internal telemetry that the service is restored.

Root cause : A recent change made to the phone number normalization logic is causing a formatting issue when users attempt to make PSTN calls in the Microsoft Teams desktop and web clients, resulting in impact.

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