The FCC has officially unveiled its proposed fines for wireless carriers over selling customer data to third parties, with T-Mobile receiving the highest fines.

The FCC’s announcement (PDF) comes after all four major carriers were found guilty of selling customer location data to third parties without consent. This arrangement violated the requirement that telecom companies be the sole gateway for the government to conduct lawful surveillance.

In at least one instance, “a Missouri Sheriff, Cory Hutcheson, used a ‘location-finding service’ operated by Securus, a provider of communications services to correctional facilities, to access the location information of the wireless carriers’ customers without their consent between 2014 and 2017. In some cases, Hutcheson provided Securus with irrelevant documents like his health insurance policy, his auto insurance policy, and pages from Sheriff training manuals as evidence of his authorization to access wireless customer location data.”

In response to public outcry from journalists, privacy advocates and lawmakers, the FCC investigated, resulting in the proposed fines. The FCC proposes fining T-Mobile $91 million, AT&T $57 million, Verizon $48 million and Sprint more than $12 million. While the proposed fines are a significant amount of money, critics have already denounced them as not going far enough.

Senator Ron Wyden, a well-known privacy advocate, was scathing in his response:

If reports are true, then Ajit Pai has failed to protect consumers at every turn. This issue came to light after my office and dedicated journalists discovered how wireless carriers shared Americans’ locations without consent. He investigated only after public pressure mounted.

— Ron Wyden (@RonWyden) February 27, 2020

It remains to be seen if the carriers will appeal the fines. Given the reaction that is already building, they may do well to simply pay the fines and move on. Meanwhile, other companies should take a lesson that it’s never a good idea to try to double-dip by surreptitiously selling the data of paying customers who expect far better for the money they’re spending.