TMobile scam to give free device

I was told I would get a free Iphone13.  I then called their customer support to verify and they communicated that it would show as a charge the first month but I would get billed and then credited the monthly cost that would equal zero.  Three months later I am still being billed and now told I would have to pay the monthly installments as it is not free.  Be sure to get anything in writing!  Now I have to go to their store and hope I find the same sales representative and supervisor that told me it would be free and hope they remember me and do not lie about their promise.