Ok, well, I finally got an old 3GS phone to work (upgraded it to 6.1.6 then jailbroke it). The sim I want to use with it (a working giffgaff sim) leaves the phone saying NO SERVICE at the top left. I've tried downloading the carrier's profile, that didn't help. And now I've tried to find the APN settings myself, to enter what the carrier states for the APN settings on their iphone page. Could it be that I've not got the SIM in properly? It's a microSim, that I've cellotaped onto a bigger sim frame to fit the 3GS. Many thanks.