The FCC first began investigating the four major U.S. carriers in 2019 after they were found selling real-time location information from customer devices to third-party data aggregators, which led to that location data being sold a second time to private investigators, bounty hunters, law enforcement agencies, credit card companies, and more.

https://www.macrumors.com/2024/04/29/fcc-fines-carriers-customer-data-sharing/