Remember the line, "Data is the new Currency", it looks like your location data is part of it - T-Mobile, Sprint, and AT&T are selling access to their customers’ location data, and that data is ending up in the hands of bounty hunters and others not authorized to possess it, letting them track most phones in the country.

T-Mobile shares location data with an aggregator called Zumigo, which shares information with Microbilt. Microbilt shared that data with a customer using its mobile phone tracking product. The bounty hunter then shared this information with a bail industry source, who shared it with Motherboard.

Motherboard’s investigation shows just how exposed mobile networks and the data they generate are, leaving them open to surveillance by ordinary citizens, stalkers, and criminals

https://motherboard.vice.com/en_us/article/nepxbz/i-gave-a-bounty-hunter-300-dollars-located-phone-microbilt-zumigo-tmobile