I have been using my iphone since Dec. 2007, I was already an AT&T customer, so I just moved my phone number to my iPhone. The phone number is on a family plan (only I am using the iphone, my parents are not). Today (Apr 27, 2008) my parents renewed the family plan contract with AT&T, they also got new SIM cards (same phone #, but supposedly more advanced cards.) Store clerk told me that my iphone will stop working unless I reactivate using the iTune. She said reactivation involves the same steps I took when I first activated the iphone. Like she said, my iphone stopped working after contract renewal. Then I connected the phone to iTune, it sync everything EXCEPT asking for activation. So I restored the phone to factory setting, then reconnect, and it said “Waiting for activation”, but after 5 minutes it said, "Activation Alert: No Signal Detected. Signal is required to complete activation." But my room ALWAYS has good signal, and this only happened after the contract renewal. Right now my iPhone says "No Service", and I canot make phone calls. Store clerk said she doesn’t know why this is happening. Help…………Any help or comment is appreciated.