Both carriers have similar programs that allow customers to carry unused data from one month to the next, but it's not as simple as it sounds. This is how these rollover data plans really work.
Though it still lags in overall number of subscribers, the carrier beat rivals last quarter in terms of gaining new customers and keeping old ones, according to a research firm.
CNET's Dan Graziano explains the difference between T-Mobile and AT&T's rollover data programs.
The Internet giant could be hoping to take another stab at going head-to-head with Apple, Amazon, PayPal, Square and a slew of other tech giants looking to grab a slice of the payments pie.
The Simply Prepaid plan puts T-Mobile in direct competition with its own prepaid arm, MetroPCS, which may actually still provide a better value for some.
A new salvo in the wireless price war cuts the price of shared data on two lines by 29 percent.
The carrier will also offer up to $350 per line to T-Mo subscribers to cover costs related to switching networks.
The carrier's "Smartphone Equality" initiative is meant to reward customers who pay their bills on time with deals ordinarily available only to those with solid credit.
The move could be the next step in Google's ever-widening ambitions to conquer the mobile world.
The prepaid carrier gives customers unlimited access to high-speed data, but with a few caveats.