You might not have to worry quite so much about carriers selling your phone location data to less-than-diligent third parties. AT&T, Sprint, T-Mobile and Verizon (Engadget's parent company) have provided responses to FCC Commissioner Jessica Rosenworcel's request for an update on the practice, with all four saying they'd halted sales to aggregators sometime after promising to do so back in June 2018. AT&T, T-Mobile and Verizon all said they'd terminated their last sales at varying points in March 2019, while Sprint said it was ending its last deal with a location aggregator on May 31st.
To no one's surprise, the carriers maintained that their sales only allowed specific uses. AT&T's terms required "approved use cases" and deletion of info, while Verizon said it had a "detailed process" for clearing and screening aggregators' customers. Sprint was less specific, but said it allowed aggregators to hold on to data for long enough to provide an "adequate response" and limited their access to just the information needed to fulfill their contracts.
It's not certain those since-ended sales were legal, though. As Ars Technica observed, the Communications Act forbids phone companies from disclosing or using location info without explicit permission from customers. There's no clear indication the networks obtained consent -- customers certainly didn't intend for the information to reach the hands of bounty hunters.
You might not get a timely response from the FCC, either. Rosenworcel wrote that the FCC had been "totally silent" about reports of companies selling location data, and Chairman Ajit Pai deferred responsibility to recently appointed commissioner Geoffrey Starks despite holding control of the investigation. Carriers may have eventually done more to respect customer privacy, but there's no guarantee they'll face punishment if they abused their power.