Today and yesterday have been terrible!
My iPhone is now constantly dropping to No Service, and when the "signal" returns on the phone, it's not actually there! Incoming calls go straight to answer phone, and if I try to call out or use data, the signal immediately drops to 1 bar, then No Service.
Off and on makes no difference.
Other phones in the 3 store (Bristol centre) were all 5 bars full signal and working fine whilst mine was out of service.
It's either something to do with the way the network allows the phone any service, or the phone itself. Got a new SIM on the way. Going to restore the phone through iTunes.
Reluctant to swap the phone as it seems more software/network related than a hardware problem.