code: public RespokeCall joinConference(RespokeCall.Listener callListener, Context context, String conferenceID) {
          RespokeCall call = null;
  
          if ((null != signalingChannel) && (signalingChannel.connected)) {
              call = new RespokeCall(signalingChannel, conferenceID, "conference");
              call.setListener(callListener);
  
              call.startCall(context, null, true);
          }
  
          return call;
      }
docs: Initiate a call to a conference.
  
  @param callListener  A listener to receive notifications about the new call
  @param context       An application context with which to access system resources
  @param conferenceID  The ID of the conference to call
  
  @return A reference to the new RespokeCall object representing this call