[BUG] No AddParticipantFailed event raised when a person does not accept a call

[Thomas-Carstensen]

Library name and version

Azure.Communication.CallAutomation 1.1.0

Describe the bug

When adding another participant to a call, mid call, an incorrect event is being sent to the application if the person does not accept the call.

If the person accepts the call the ParticipantsUpdated and AddParticipantSucceededis being sent correctly.

But if the person declines the call no AddParticipantFailed event are sent and the ParticipantsUpdated event shows the two phone numbers and the ACS instance in the call, when in fact there are only one person and the ACS instance in the call.

Expected behavior

Expected an AddParticipantFailed event and that the ParticipantsUpdated event shows corret amount of members in the call.(one person and the ACS instance)

Actual behavior

Sends AddParticipantSucceeded event and the ParticipantsUpdated event shows two persons and the ACS instance

Reproduction Steps

1. Start call to ACS.
2. Add another person to the call.
3. Second person declines call.

  var callerIdNumber = new PhoneNumberIdentifier("+4512345678"); 
  var addThisPerson = new CallInvite(new PhoneNumberIdentifier("+4587654321"), callerIdNumber);
  
  var addParticipantOptions = new AddParticipantOptions(addThisPerson);
   await _callAutomationClient.GetCallConnection(callConnectionId)
      .AddParticipantAsync(addParticipantOptions);

Environment

Azure Communication Service
Danish phone number (+45)
Event Grid System Topic (Microsoft.Communication.IncomingCall)
Event Subscription (webhook)
REST API with .NET 6

[github-actions]

Thanks for the feedback! We are routing this to the appropriate team for follow-up. cc @acsdevx-msft.

[Thomas-Carstensen]

@jsquire After further testing, my team may have found the source of the issue. The theory is that if the third person has an answering machine or service, the call is seen as aswered because of the automatic voice telling you to leave a message.

Im not sure if ACS or the CallAutomation package is able to handle this as i have not found information about this in the documentation