Hi: I have read some posts about iphone got 'no service' or dropped from 5 bar to no service. I have got same experience last week and finally solved it (by changing to a new iphone). Here is my story: I got my iphone on the first day (Friday) and then activated it. Everything works perfectly. Then from the second day (Saturday) I occasionally got 'No Service'. At first I thought it was due to ATT's bad coverage in school. But from the forth day (Monday) I totally got no signal anywhere. So I went to the local ATT store on Tuesday. The manager helped me to change a new SIM card and everything was fine: I could make calls and using every functions. I thought the problem was solved by changing a new SIM card. But one day after changing the new SIM card, the iphone got 'No Service' again! I was using EDGE to browse the web when the iphone still had 3 bar signal, then suddenly the signal dropped to 0 and iphone showed 'NO Service'. After that I made calls to Apple tech support and ATT support. I have spent over 3 hours on the phone and talked to over 10 representatives. They have tried everything like: reset phone setting, restore iphone, reset information from ATT... I also changed SIM card again. But no help. Finally the Apple thought maybe it is due to the defects from this iphone. They helped me to contact a nearby Apple store which still has some new iphone available, and changed my iphone on Friday. It just took 10 mins to change it. And from that on, all the problems solved! From Friday up to now, it never shows 'No service', and I have used EDGE and made calls for over 8 hours and got no problem. So for those who are still troubled by this problem, ask ATT/Apple to change the SIM card or iphone.