Security Of My T-Mobile Account?

I need help trying to get support from T-Mobile on fixing my account ownership. A while ago I started receiving texts about account payments but the name on the account was for someone I've never heard of. For the past several months I've been trying to get someone from T-Mobile to fix this for me to no avail...they say they will address it, then crickets. To add insult to injury, when recently trying to add a device to one of my lines, T-Mobile told me I could not do so because I was not the account owner...even though I've had this account for over 8 years and have paid for and managed it for that entire time.

Not only am I questioning the security of T-Mobile, but I'm also questioning the quality of their customer support team and staff (online and in person.) Given the severity of my personal information being affected, do I seek legal or social media support at this point?...can someone please help. I welcome any/all advice. ¡Gracias!