Anyone else have this problem where the network bar is replaced by 'No Service'? My iPhone 4 does this occasionally and I have to restart my phone to regain service, airplane mode doesn't fix it, only a restart. Can't make calls or sms during this time. I have had my iPhone replaced, not for this reason, but even the previous one did this. It does this on average about once or twice every 2 weeks or so, sometimes more frequently. I've googled the problem and seems to be a common one, however I haven't seen any fixes...