Based on http://developer.android.com/refere...dioCall.Listener.html#SipAudioCall.Listener() , there should has a CallBusy or callcanelled event which will be used for example, sip ua A called sip ua B but B rejected the call, sip ua A should receive this event. Without this event sip ua A has no way to know this call was already being rejected.
Sir, I just downloaded and installed B4A version 3.0, I still could not find oncallbusy event for sip object. So, it does not be implemented in version 3.0 yet. Correct me if I am wrong.