code: public boolean sendMessageResponse(int statusCode, String reasonPhrase, int expires) {
      return sendMessageResponse(statusCode, reasonPhrase, expires, null, null, null);
    }
docs: This method sends a basic response to a previously received MESSAGE request. The response is
  constructed based on the parameters passed in. Call this method after waitForMessage() returns
  true. Call this method multiple times to send multiple responses to the received MESSAGE. The
  MESSAGE being responded to must be the last received request on this SipCall.
  
  @param statusCode The status code of the response to send (may use SipResponse constants).
  @param reasonPhrase If not null, the reason phrase to send.
  @param expires If not -1, an expiration time is added to the response. This parameter indicates
  the duration the message is valid, in seconds.
  @return true if the response was successfully sent, false otherwise.