Optional: notify the server that the user is currently busy in a call: this will automatically refuse all incoming phone calls until the current phone call is ended.
boolFalse#bc799737 = Bool;
boolTrue#997275b5 = Bool;
phone.receivedCall#17d54f61 peer:InputPhoneCall = Bool;
||The phone call we're currently in
||The call was already declined
||The provided call peer object is invalid