Nothing I have been through 3 of them now. This one finally works like it should. My gf lives with 2 other roomates who have them I would have no service they would have full service. One day I litterally went from 3g service, to Edge service to no service in a matter of 4 min. Its a joke. this new one has been great but I have only had it for a week, and am yet to fill it with apps