Im getting billed on games on google play on a tablet i dont own

This all probably started in 2023 or 2022 but I didn't notice that some I don't know add a watch and tablet to my account and recently I noticed that someone is charging me gems and other things on a game called Free Fire: The Chaos on google play they have probably spend more than 200+ worth of in game stuff. I decided to solve this and go to a T-Mobile store and when I told them my situation they didn't believe me and though I was the one that owned both the watch and tablet so they didn't help me with my problem. Recently I have called T-Mobile to try and help me but they either don't believe or say they have blocked the transactions they don't work I stops for a while and when the transactions start again and I also tried to contact the fraud department but there no help I don't know what to do now there wasting my money I want to find who's behind all this. Do you guys have any suggestions?