I suspect that Verizon, T-Mobile and AT&T also have data.
Verizon bought AOl, HuffPost, Techcrunch and plenty of other media to build an advertising giant by pairing data with sites audience -- and took 4.6 BILLION WRITEDOWN on the whole venture [1] because failed to make it work.
[1] https://www.recode.net/2018/12/11/18136127/verizon-aol-yahoo...
EDIT: oh and AT&T will learn the same lesson with their recent 800M AppNexus aquisition. Just give it time.
https://www.engadget.com/2019/02/07/carriers-were-selling-yo...
> Carriers sell information about you to data aggregators, which normally require the user to consent before selling it on further. But some third parties opted to sell information, like people's whereabouts, on to bodies such as bail bond companies, bounty hunters and landlords. In its original report, Motherboard paid an bounty hunter $300 to get the location of a phone to within a few hundred meters.
It has been illegal for them to do so until relatively recently.