• by Wendy Davis  @wendyndavis, October 19, 2016

T-Mobile will pay $48 million for throttling customers with "unlimited" data plans, the Federal Communications Commission said Wednesday.

The sanction stems from the carrier's practice of slowing down the mobile broadband connections of its heaviest data users when the network was experiencing what T-Mobile calls "contention" -- apparently a precursor to "congestion." The FCC alleged that during periods of contention, T-Mobile throttled customers who exceeded usage caps in a given month. In some cases that cap was 17 GB, according to the FCC.

The agency says T-Mobile's practices violate a 2010 rule requiring carriers to disclose their broadband practices to consumers.

"In order for consumers to choose and use the Internet service that best fits their needs, they must not be subjected to the caprice of undisclosed restrictions that mislead them or contradict representations from providers about their broadband Internet access service," the FCC's enforcement bureau said in its order.

T-Mobile also agreed to make "clear and conspicuous disclosures" about data restrictions on its plans, or to refrain from using the word "unlimited" to describe plans that throttle users who hit a cap.

The FCC says it began investigating T-Mobile in March of 2015, after receiving complaints by consumers. Four months later, T-Mobile reportedly revised its disclosures to say that people with "unlimited" data who consume more than 21 GB in a month may be "deprioritized."

This August, T-Mobile rolled out a new "unlimited" data plan that automatically throttles all streaming video to 480 lines per screen -- enough to watch in standard definition, but not high-definition -- and that slows people's connections after they hit a cap of 26 GB in a month.

T-Mobile isn't the only carrier to throttle users with unlimited data. AT&T previously slowed down its unlimited subscribers after they hit caps of either 3GB or 5 GB, depending on their type of device. (AT&T now throttles users after they consume 22 GB of data in a month, when the network is congested.)

Last year, the FCC proposed that AT&T pay $100 million for its former throttling practices. The telecom is fighting the sanction.

In T-Mobile's case, the $48 million sanction includes a $7.5 million fine and $35.5 million in benefits -- a combination of discounts on accessories and extra data -- for customers.