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Place server-initiated outbound calls with Teams Phone Extensibility

Teams Phone Extensibility (TPE) lets applications place outbound calls through Microsoft Teams by using Call Automation APIs. Use this capability to automate customer notifications, enable callbacks, or integrate calling into workflow systems.

Beginning with Call Automation version 1.5.0‑beta.1, you can call the CreateCallAsync API to place outbound calls to PSTN numbers or Teams users from a server-side application.

Prerequisites

Before you begin, ensure the following:

  • Install Azure.Communication.CallAutomation version 1.5.0‑beta.1 or later.
  • Have:
    • A Teams Resource Account to use as the caller identity.
    • The Object ID (OID) of the Resource Account.
    • A valid callback URI to receive call events.
  • Review:

Licensing requirements

Starting November 1, 2025, Calling Plan licenses assigned to Teams Resource Accounts will no longer support On-Behalf-Of PSTN outbound calls or server-initiated outbound calls. A Pay-As-You-Go Calling Plan is required for these scenarios.

Note: Direct Routing numbers aren’t affected by these licensing changes.

Calling Plan customers

Assign a Pay-As-You-Go Calling Plan license to any Teams Resource Account that uses a Calling Plan number for outbound PSTN calls. Outbound calls will fail after November 1, 2025, if licenses aren’t assigned. You can follow the below steps to make sure you get the proper licenses:

  1. Log in to the Admin portal
  2. Verify agreement type and funding source
    • For MCA agreements:
      • Confirm postpaid payment method is active.
      • Navigate to Marketplace → All Products.
      • Search for Microsoft Teams Calling Plan (Pay-As-You-Go).
      • Select the appropriate Pay-As-You-Go Calling Plan Zone (Zone 1 or Zone 2) based on your location.
      • Add the plan under Add-ons.
    • For older agreements:
      • Navigate to Marketplace → All Products and purchase Communications Credits.
      • Add funds to ensure a positive balance.
      • Enable Auto-Recharge under Billing → Your Products → Communications Credits.

Operator Connect customers

Starting November 1, 2025, On-Behalf-Of PSTN outbound calls and server-initiated outbound calls may change depending on your carrier. Work with your Operator Connect carrier to ensure uninterrupted service. Without carrier adjustments, outbound calls through Teams Phone Extensibility may fail.

Learn more

How it works

  1. Create a CallInvite by using a target phone number or Teams identity.
  2. Set TeamsAppSource to the Resource Account OID.
  3. Call CreateCallAsync on the CallAutomationClient.

You’ll receive the following events:

  • CallConnected – the call was established.
  • ParticipantsUpdated – provides the current participant list.

If the call fails, you’ll receive:

  • CreateCallFailed
  • CallDisconnected

Code example (C#)

public async Task PlaceOutboundCallAsync(string targetPhoneNumber, Uri baseUri)
{
    // Initialize CallAutomationClient with your connection string
    var client = new CallAutomationClient("<resource_connection_string>");

    // Convert target phone number to EL64 format if required
    PhoneNumberIdentifier callee = new PhoneNumberIdentifier(
        Helper.convertToEl64(targetPhoneNumber));

    // Create the CallInvite
    CallInvite callInvite = new CallInvite(callee, null);

    // Configure call options with TeamsAppSource (Resource Account OID)
    var options = new CreateCallOptions(callInvite, baseUri)
    {
        TeamsAppSource = new MicrosoftTeamsAppIdentifier("00000000-0000-0000-0000-000000000000") // Replace with Resource Account OID
    };

    // Place the call
    CreateCallResult result = await client.CreateCallAsync(options);

    // Use result.CallConnection for further actions (play audio, transfer, etc.)
}


sequenceDiagram
    participant App as Customer's Application
    participant CallAutomation as Call Automation API
    participant PSTN as PSTN Endpoint

    App->>CallAutomation: CreateCallAsync (CallInvite, TeamsAppSource)
    CallAutomation-->>App: CreateCallResult (CallConnection)
    CallAutomation->>PSTN: Initiate outbound call
    PSTN-->>CallAutomation: CallConnected
    CallAutomation-->>App: Event: CallConnected
    CallAutomation-->>App: Event: ParticipantsUpdated
    Note over App,CallAutomation: If failure occurs
    CallAutomation-->>App: Event: CreateCallFailed + CallDisconnected

Next steps

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