I have been told that on some networks that the iPhone has just come out on (e.g: Orange, VODAFONE (the one I'm talking about)). If not, will they work if you jailbreak it?
Yep. the iPhone only comes with an O2 sim and is locked to that. However if you jailbreak it, not only can you choose any network you want, you can also download free apps and they work every single time!
