Not sure if this is a repost but I did use the search facility before creating this thread. I've got an 8GB iPhone 3G that I've owned for around about a month and so far I've had no problems, up until late this afternoon when my signal bars completely disappeared. Ever since I've had a no service message in the top corner of the screen, despite another mobile phone on the same network having a full signal, sat right next to the iPhone. Every other function of the phone works fine, including the browser, iPod, Mail and all the other Wifi features. I've so far tried powering off the iPhone, resetting by holding down the minimize button and the power button, taken the SIM out and put it back in, I've tried turning Airplane mode on and off which was suggested by someone, I also tried resetting the network settings by going to Settings > General > Reset > Reset Network Settings. None of these have worked so I thought I'd go for a last ditch attempt at restoring the iPhone completely. After I backed up all my stuff I restored the phone through iTunes, upon turning the phone back on I had a message telling me something along the lines of: "Waiting for activation, this may take some time". I've absolutely no idea what's happened and nothing has changed on the iPhone apart from me changing to a different tariff a few days ago, maybe it's possible that the tariff I have switched to isn't supported by the iPhone? I'm not sure, anyway, people have advised me to take it to an Apple store and with the nearest one being some 30 miles away I'd rather ask here before I commit to driving to the shop. The iPhone is just over a month old, was brand new when I bought it from O2, has not been unlocked or jailbroken, is on an O2 3G PAYG SIM, which has worked since the day I bought the phone. The only changes have been a change that I made to my tariff a few days ago and that is the only thing I can think of that may have made this happen. If anybody has any advice or things that I can try then I'd be more than happy to hear from them.