Hello there, you might want to reach out to T-Force via Twitter or Facebook to check if you ever had a handset research form filled on your account, and if not, they can submit one for you. This is the only way to zero out your account. Once that happens, a review can be submitted to have the account removed from the account agency, if possible.
Someone may have made an account with your SSN. I had mine stolen, a fraudulent account was made and eventually some bills from that account went to collections, all without my knowledge (my account was always paid). It happens, T-mobile doesn't verify identity when folks sign up.