I reviewed your code and if you do the following you should be able to get the data you need. You need to be aware that object that always need to be parsed before passing the array to a view. In your case you didn't do that.
success: function (msg) {
var Obj= eval(msg["d"]); or // $.parseJSON(msg["d"]) Method to evaluate Json
$.pnotify({ //CALL PNotify
title: Obj["0"].NotificationText, // The pared arrays
text: Obj["0"].NotificationDescription