It’s official: T-Mobile has gotten under ATT’s skin. ATT announced on Friday that it will offer T-Mobile customers up to $450 per line when they switch to T-Mobile, 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. ATT Offers T-Mobile Customers Up To $450 Per Line To Switch DALLAS, Jan. 3, 2014 /PRNewswire/ – Starting today, ATT* is offering T-Mobile customers the opportunity to upgrade their mobile