For anyone who uses AT&T as one of their carriers, here are a few links I’ve used to opt out of them selling my info. I obviously don’t trust them as far as I can throw them, but it’s a nice start, even if placebo.
https://att.com/privacychoices - Privacy Toggles
Restrict the use of my CPNI for marketing - CPNI Restriction
Your Privacy Choices - Opt out of the sharing and selling personal information
Data Request Center - If you want to know what data they already have on you.