It’s official: T-Mobile has gotten under AT&T’s skin. AT&T announced on Friday that it will offer T-Mobile customers up to $450 per line when they switch to AT&T, a stunning preemptive strike that’s being done in response to a rumor that T-Mobile plans to pay off subscribers’ early termination fees when they switch from another carrier. The $450 payout will include the standard $250 that switchers can receive when they trade in their old device as well as an additional $200 payout specifically aimed at T-Mobile subscribers. The company’s full press release follows below: "Starting today, AT&T* is offering T-Mobile customers the opportunity to upgrade their mobile lifestyle with value of up to $450 per line when they switch to AT&T and trade in an eligible smartphone." Read the full story at Boy Genius Report.