[iMore.com]

AT&T is offerring a $100 bill credit to new and existing customers that add a device to their plan, including smartphones and tablets. For iPad users, this is on top of the $100 discount you get when buying a new iPad through AT&T with a two year commitment. Customers will get $100 taken off their bill for each new device they add.
The offer is open through March 31.
AT&T coverage map
Source: AT&T

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