scammed by tmobile

This December i have call on customer service just asking them unlock my samsung 23. The guy on the call said that there is a holiday promotion goin on and you are  qualified for it . Promotion was suppose to be since i had two lines on my account if I add the "3rd" line on my account i will get the third line for free and 830$ off towards any phone purchase . I said ok i was thinking to add another line on my account so why not , so i took the offer . And ordered a new iphone 15 pro Max 256gb and the next month guess what happened? I got billed for the line and the phone in total of 100$ and from the last 5 months i m getting billed the same till now . I called the customer service more than 10 times they still dont be able to figure out anything as of now . And still i m gonna get billed next month also never goin have t mobile again once this is all over