I'm traveling to Singapore this coming week and will be there for 2 weeks. I saw that the local TelCo sells SIM cards but was wondering what I would need to do to make it work in the iPhone - do I need to register it with iTunes or do something else to activate it? If so, then what happens to my apps, data, music, pix and videos? Any help is appreciated.
I purchased a SIM card when I was in Iraq for a cheap nokia. It was pre paid and you used the network on which the SIM was purchased. You should also get a new number. Other than phone services i'm not sure what else you'll be able to do.
If you are in the US your iPhone is carrier locked to AT&T and will not work with another SIM card. You would need to jailbreak + unlock it to work with a local SIM. If you don't want too your best bet is to pick up a cheap unlocked phone for calls and use wifi for data.