I've bought a 2nd hand Iphone 3gs, and i'm pretty new to it all.
I currently use a tesco sim only 500mins etc £10 a month.
The phone I bought is on o2, and works with my spare o2 sim card, however when I put the tesco one in, it comes up with 1 bar of signal, but doesn't find a network.
Can anyone explain this?
Is it possible to unlock this using a program?