For quite some time now, T-Mobile has been, on and off, selling data plans that were supposedly unlimited. These plans were touted as giving the user all the 4G LTE speed that they could use. Users ended up more than a little surprised to find that after using a certain amount of data, said by the FCC in their report to be 17GB, customers were finding that their speeds hit such low levels that their service became "unusable", much like a fixed data customer may experience when throttled. Rather than being throttled to a fixed speed, however, these users had been deprioritized; in short, when the network got congested, their traffic was reduced in order to ensure that the network could handle other users. The issue here is that, up until June of 2015, T-Mobile never fully disclosed that this was the case, and the FCC did not take kindly to that.
The FCC launched an investigation into the practice, during which they received multiple complaints from users about not knowing that they, effectively, had a data cap. While the actual practice of deprioritization is technically fair game, this is only the case if customers know about it. According to the FCC, T-Mobile was not doing enough to ensure that customers who used buckets of data knew what they were getting themselves into. The FCC has imposed a $48 million payout upon T-Mobile, along with other stipulations effective immediately
While T-Mobile did change their disclosure in June of 2015 to more accurately reflect the nature of their data plans, the FCC's requirements mean that T-Mobile must also offer T-Mobile and MetroPCS customers a discount of 20% on any accessory on a one-time basis, and provide an extra 4GB of data to all customers who were affected, but have another line on their plan using a limited data plan. Customers will be notified of these perks by December 15. As for the $48 million payout, $7 million of that will be in the form of a standard fine, while $5 million and any part of the remainder that's not spent on customer initiatives as outlined above will go toward providing free devices and cheap service to schools, starting in October of 2017.