Problem with iPhone 4 (8 GB): the cell phone/SMS/3G function works intermitently... Since 30 days ago, at least once per day I have to turn-off and turn-on the iPhone, and then it starts working again... 1. I changed the SIM card at a Koode service center 2. I restored to factory settings the iPhone 3. Apple changed me the iPhone for a brand new iPhone 4 It stills do the same thing... Please advize.