If you want to have an iPhone with a different phone carrier than AT&T, you’ll need to unlock your iPhone. Follow these options to unlock your iPhone, and you’ll be free to use any cell phone provider you wish.
How to Unlock Your iPhone
If you are technically inclined or have some patience, you can try to unlock you iPhone yourself with the help of some programming tutorials online. There are written and video tutorials online so you can study the entire process before attempting to do it yourself.
Alternatively, you can buy a program from one of many providers of iPhone unlocking software for about $15 - $30. Go to Google.com and search for “unlock iPhone” or “unlock iPhone software.”
Ask technically-savvy friends and electronics store associates for their help. If you know anyone who loves iPhones and Macs, they may be able to assist you or point you to more resources. Search online for community groups and forums for more information. You may be able to email someone who’s recently gone through it for help and make a new friend in the process.
If you have a new iPhone that you could return to the store, then you could return the locked iPhone and purchase one that is already unlocked from eBay.