I suspect this may have been asked before - apologies if so and I'm the only person not to know about this but.....my iPhone 4 (which is a year or so old) has started dropping the signal and then refusing to reconnect until I turn it right off and then on again. Switching to Airplane mode doesn't jog it back into life; it has to be a hard re-set.
I haven't dropped or knocked it, and it's in a case that's supposed to get round the infamous 'holding it wrong' problem.
I'm on Vodafone PAYG and I don't know whether it's likely to be a Vodafone issue or a phone one. Thing is, I'm desperate to import my previous number from another network but I don't want to do that until I've narrowed down the problem. If it's a Vodafone thing then I might have to change networks. If it's the phone, I guess I'll have to take it into an Apple shop to get it looked at 
Thanks in advance for any help....