Buy your iPhone from Apple commitment-free.
It works with the carrier of your choice. Buy your iPhone from the Apple Online Store and choose your own GSM carrier. You can change carriers at any time.
It’s easy to set up. Get a compatible SIM (iPhone 3GS) or micro-SIM card (iPhone 4) and select a plan from the carrier of your choice. Then insert the card and set up your iPhone using iTunes on your Mac or PC. With a few clicks, you can start making calls.
It works internationally. Because this iPhone is commitment-free, you can purchase a micro-SIM or SIM card and service from a local carrier at your destination. Or check with your home carrier regarding international roaming charges.
thats what i got from apple.com