...or do i need other iphone plans? I am buying an iphone 2g off of ebay. i have a 3g sim card (smartchip). To use the iphone, do i just have to put in my sim card and will it work normally? Or do i need to sign different contracts with apple or something. What do i need to do or can i just use my regular 3g sim card and plug it into the phone and it will work normally. please respond soon.