To do so you will need an already activated AT&T Sim card. If the sim card has not already been activated, a.k.a, brand new sim card, it will not work. You may purchase one easily from eBay.
- Power on the iPhone
- Start iTunes on your computer
- At the Emergency call screen, insert the sim card into the iPhone.
- Connect the iPhone to computer via USB cable.
- Wait 2 minutes or so.
- It should get past the emergency call screen. If it does not, disconnect the USB cable and reconnect. It should work then.
- This works for iPhones from all carriers. If the iPhone was purchased from Rogers for example, you will need a used/activated sim card from Rogers.
- The sim card must NOT have a passcode over it. Otherwise it will not work.
- if iTunes prompts you for the billing address zip code and last 4 digit of SSN number of the iPhone owner, it means that the sim card is current associated with another iPhone. You will need another sim card to activate the phone.