AT&T announced today that is now offering T-Mobile customers up to $450 in credits to switch their phone service over to AT&T. The deal, available for a limited time, allows T-Mobile customers to switch to AT&T and trade-in their current smartphone for a promotion card of up to $250 that can be used toward AT&T products and services, with the actual value of the trade-in based on the make, model, and age of the user’s current smartphone. AT&T will also offer an additional credit of $200 per line for T-Mobile users who transfer their wireless service to the carrier and choose a NextSM plan and either buy a device at full retail price or active a device they already own.