Got an iPhone 4S today from AT&T, activated all was well until I started playing with Siri and a couple minutes later the phone got quite hot. I got a Bad SIM messages. The phone now says No Sim even though the sim is inserted. I have since tested the 'bad sim' in my old iPhone 4 and it works. I then put in a new SIM into the iPhone 4S, but it still says NO SIM. Is this a known fault with iPhone 4S?