Switch from T-Mobile to AT&T and the nation's second largest carrier will give you as much as $450. Some of that sum comes from a promotion card that AT&T will give you for trading in your current smartphone. The card must be used for AT&T products or services, and the actual amount you'll receive will be determined by the age, condition and model of the phone you trade in.
The remaining $200 is awarded to T-Mobile customers who jump to AT&T, sign up for AT&T Next and purchase a new device at full price or have a phone activated that they already own. AT&T Next is the plan that offers an early equipment upgrade to customers who make at least 12 monthly payments toward a new phone purchased at the full retail price.
Sounds like at least one major U.S. carrier hears footsteps behind them, and is peering over its shoulder.