My activation was a little weird, the guy that I was talking to on the phone at AT&T didn't seem to know what he was doing exactly, but my phone was activated. After a while I received this "No SIM" error and I'm like WTF. I popped out the sim, rebooted, etc. to try to fix it. It would only work for a short amount of time before I had the No SIM error once again. So I did a complete restore on my iPhone 4 and it seemed to fix it until about a day later when I got the error again. Anyways, who do you think I should contact. Apple or AT&T? I just want to get this problem fixed, I don't want to pop out my SIM and reboot every 10 minutes. Anyone else have this problem too?