The iPhone can be purchased at all US Apple Stores, at select AT&T stores, or online (http://store.apple.com). Both Apple (http://www.apple.com/retail/iphone/)and AT&T (http://www.wireless.att.com/find-a-store/iphone/) offer online locators to help you find stores that stock the iPhone and check availability. If checking availability at an Apple store, you should check after 9 P.M. the night before purchase since this is when most Apple stores close and availability is updated.
If you have general questions about AT&T's contract terms, billing, or service availability in your area, you might find it helpful to visit an AT&T store (or check online at http://www.wireless.att.com/cell-phone-service/specials/iPhoneCenter.html ). Also, when buying from AT&T, sales representatives can run a preliminary credit check for you, saving you a step (and potential surprises) when activating an iPhone at home.
Activation Through iTunes
Once you've bought your iPhone, you'll need to activate it through iTunes. This may seem strange for most cell phone users, but the process is typically smooth and straightforward. First, ensure that you have the most recent version of iTunes (http://www.apple.com/itunes/) and then connect the iPhone to the computer. iTunes will launch and begin the activation process.
You'll be asked whether you are an existing AT&T customer and if so, whether you're replacing an existing phone or adding a new line. If you're a new customer, you'll have the option of activating a single iPhone or multiple iPhones with a single new account.
New customers will be asked if they want to transfer an existing phone number from another carrier. This process, which is known as porting, can take anywhere from a few minutes to a few hours if there are no problems. Porting requires you to enter the number you want to transfer, the wireless account number with the existing carrier, billing ZIP code, and account password or PIN.
The porting process actually requires your existing carrier to approve the transfer. Most porting failures result in issues with the account password and require calls to a specific group within AT&T support to resolve. To avoid problems, you may want to verify your account password with your current carrier before beginning the activation process. AT&T also verifies the area code of the number with your billing ZIP code and typically doesn't allow you to port a number from one area code if you enter a ZIP code outside that area code (some users have reported just entering an appropriate ZIP code that is different from their actual ZIP code allows the port to continue).
Next, you'll need to choose a plan and enter your Apple ID (the same ID that you would use to buy music or videos from the iTunes Store). After that, you'll enter your personal and billing information for a credit check. If an AT&T store has pre-screened your credit, you can enter a code provided on your iPhone receipt, although you will still need to provide your social security number. If you fail the AT&T credit check, you'll be given the option of choosing a month-to-month plan.
When you're done entering information, iTunes will verify and process your activation. At the end of this process, iTunes will display your phone number and your iPhone will alert you that it has been activated successfully.