AT&T will begin a program tomorrow that offers at least $100 off the purchase of a smartphone when a customer trades in their current AT&T smartphone. The offer applies to any smartphone sold by the carrier, including the iPhone. According to AT&T:
This promotion applies to any smartphone AT&T sells, and gives customers access to the latest devices at a fraction of the cost or, in the case of smartphones priced under $99.99**, for free. To take advantage of this offer, customers are encouraged to visit any AT&T company-owned retail store or participating authorized dealer with their previous smartphone that is no more than three years old and in good, working condition. In stores, upon trading in their old phone, customers will receive the $100 credit on-the-spot and can use it immediately.
Phones valued at under $100 will be available for free with a new contract. The credit can also be applied towards accessories. Customers will be able to trade in any smartphone as long as it is no older than three years, and is in good condition. The promotion will last for a limited time, though AT&T has not clarified when it will end.