Originally Posted by
jackal
Your iPhone 4 should work if it's an AT&T phone (I did the same with my old iPhone 4, which I then used with a Claro SIM in Peru). However, you'll need to get AT&T to unlock it before you leave. You might be able to do that by going to an AT&T or Apple store; otherwise, you may need to do some research online to see how to get it unlocked by AT&T over the phone since it's no longer your active phone. Those instructions are probably a bit beyond the scope of this thread, but it should be doable.
I'm sorry, I don't know what a Holiday Phone is.
Okay - cool. Called AT&T and got my old iPhone4 unlocked. Just connected to iTunes and backed it up.
By all counts - I should now be able to put a prepaid UK micro-SIM into it and use it while I'm in the UK? Hope so!