Microsoft has acknowledged a service disruption affecting Microsoft Teams that is preventing some users from making or receiving voice calls. The company posted an incident notice on its Microsoft 365 Status channel on September 21, 2026, and labeled the issue under the incident ID TM1475580 in the Microsoft 365 admin center.
What’s Known (and What’s Not)
The advisory from Microsoft is limited in scope: only “some users” are impacted, and there’s no clarity yet on which regions, customer types, or specific call formats (e.g., PSTN vs internal Teams-to-Teams) are affected. The root cause, duration, and full scale remain unspecified.
While the problem seems focused on Teams calling features, the company didn’t suggest that other Microsoft 365 services—chat, meetings, file sharing, identity verification, etc.—are compromised. Organizations should therefore assume those functions remain operational unless their internal logs or telemetry indicate otherwise.
Guidance for Businesses and IT Leaders
IT administrators are urged to log into the Microsoft 365 admin center and review incident TM1475580 for updates relevant to their tenant. Tracking metrics like affected client apps (desktop, web, mobile), geographic locations, error messages, and call direction (incoming vs outgoing) will be vital for diagnosing impact.
Rather than rushing into configuration changes, companies should rely on resilient communication plans. Alternatives like PSTN lines, corporate mobile phones, emergency conference bridges, or other approved channels can help maintain continuity during the outage. Leaders should also remind staff not to use unapproved tools or channels, particularly for sensitive or crucial discussions.
On the security operations front, a failed or disrupted call should not automatically be treated as a sign of a cyber breach or account takeover. Correlating user reports with internal network, endpoint, and identity logs—and Microsoft’s own status feeds—is essential before jumping to conclusions.
Microsoft has confirmed that the investigation remains active. Administrators are advised to communicate the confirmed scope to internal stakeholders, keep updated via the incident record, and retire any temporary fixes once Teams calling functionality is fully restored.
This outage underscores the fragility of relying heavily on cloud-based communication platforms. When Teams voice goes down, front-line support, incident escalation, and executive dialogues can all grind to a halt. Moving forward, companies will need more robust redundancy, clearer escalation paths, and improved visibility into vendor service statuses—so that when “service unavailable” becomes a reality, the damage is limited and the recovery swift.
