NgnMessagingSession instantMessagingSession = NgnMessagingSession.createOutgoingSession(
  VoiceCallActivity.getInstance().getNgnSipService().getSipStack(),
  remotePartyUri
);

if (!instantMessagingSession.sendTextMessage(messageEditText.getText().toString())) {
  Log.e(Constants.TAG, "Failed to send message");
} else {
  String conversation = conversationTextView.getText().toString();
  conversationTextView.setText(conversation + "Me: " + messageEditText.getText().toString() + "\n");
  messageEditText.setText("");
   Log.d(Constants.TAG, "Succeeded to send message");
}
NgnMessagingSession.releaseSession(instantMessagingSession);