code: public void cancel(String[] protocol, int[] reasonCode, String[] reasonText) {
  		if(ackReceived) 
  			throw new IllegalStateException("There has been an ACK received. Can not cancel more brnaches, the INVITE tx has finished.");
  		cancelAllExcept(null, protocol, reasonCode, reasonText, true);
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.Proxy#cancel(java.lang.String[], int[], java.lang.String[])