Type of call transfer - Attended or Unattended.
Assembly: Microsoft.Rtc.Collaboration (in Microsoft.Rtc.Collaboration.dll)
In Unattended type, the call is terminated as soon as the transfer request is accepted by the remote participant.
In Attended type, the call monitors the success/failure notifications from the remote regarding how the transfer is being carried out.
If the transfer succeeds, this call is terminated otherwise, the call state is not affected.