Hi all, I've just bought a second-hand iphone 5 which has a problem. I was told that it was originally on O2 contact (I don't know how to check that) but it came with a GiffGaff pay as you go (I think) SIM. It says at the top "O2-UK" and I've seen "3G" come up next to it, but I don't get any signal bars. I've checked to see if the IMIE was blocked and it's not, plus I believe if it was blocked it would just say "NO SERVICE". I've seen one bar appear on the signal bar, which would maybe make you think it was an antenna problem, but where I live the reception is really poor and it still comes up O2-UK, so the antenna must be good. I should add that I have try the phone in a strong signal area and it still has no signal. Any suggestions would be much appreciated.