I'm about to upgrade from the iPhone 3G to the iPhone 4, and I'm not sure what will happen to my old device once my phone number is transferred.
Specifically, I want to give the old device to my girlfriend, who is on a AT&T non-smartphone. What will I have to do to move her to the iPhone 3G? Will she need to sign up for an iPhone specific data plan if I put the sim card in there? WIll it work like any old phone if I just put the simcard in there?
In short, I'm not sure what will happen, and what I need to do.