This is a carrier in the USA (T-Mobile).
I did a quick search for the other 2 carriers using the term “[Carrier Name] Family Tracking” and Verizon and AT&T also seems to have it.
And according to https://www.t-mobile.com/support/plans-features/t-mobile-familywhere-app, it says:
FamilyWhere uses geolocation data from the T-Mobile network and is not affected by changes to device location settings.
So it appears that its using cell tower triangulation. Turning on Airplane Mode should stop it (assuming there isn’t a separate tracking app on your phone)
Oh Wow, What a wonderful tool for abusive spouses and abusive parents. And telecom companies are making money off of it. 🙃
TLDR: Its a good idea to get your own separate cellular plan.
The counter argument on this is, you need to be an authorized person on the account to enable and considering authorized people are the people who are paying the bill they have full control. In the eyes of the Telecom the authorized user owns every device that’s on the account so they say they want to track it they’re allowed to track.
If you’re worried about privacy and someone tracking you that’s part of your plan, you need to isolate into a separate plan. You lose so many areas of privacy by being on someone else’s plan, like the saving money is nice but they can look up your call history, some carriers allow you to look up SMS history it’s not good