I use it since they launched it on facebook. I have never seen a better calling upp.
The rates to call mexico are really low (1.4 us cents per minute), it is really the best you can gate for calling mexico!
Before I have used the hello mexico phone card wich is also great, but it had a greater rate than nobelapp.
Both phone card and the app has great call quality moreover with the calling app you can use WIFI to call.
This is really convenient when you travel abroad, because you can find WIFI everywhere. I recommend them with all my heart.
Review about: Nobelcom Phone Service.