If you get a call on ts3 mobile, you fly out of the ts client in the background, it immediately leaves the server and you have to come back in by hand, this is very annoying if you are charging your phone and have dirty hands, so you have to end the call again, then run back and reconnect to the server.
a better alternative would be to stay connected in the ts client, but mute mic & sound, and unmute it after the call.