We see a positive improvement and we will close this incident on our side. More information about the root cause can be found in the Microsoft Service Health page under incidentID TM677554

Since this morning we received several notification of Microsoft rejecting calls with an error "Service unavailable". Due to this Microsoft 365 issue Voice365 customer might have a degraded performance on their Teams service affecting inbound and outbound calls.

Microsoft has acknowledged the issue in TM677554 (Users and external PSTN callers may intermittently be unable to reach resource accounts) which can be accessed by your tenant administrator.

Our partners are able to set advanced failover forwards on your numbers to prevent the unreachability of your organisation. This advanced failover feature, when enabled, will be activated automatically when Microsoft has a similar issue in the future. The Advanced failover forward will automatically be deactivated when Microsoft has resolved the issue.