Dissatisfied Customer!!

I went to t-mobile this spring to open my first phone account, i asked the cells man how much it would be for an apple watch. So he added it to my account to see how much the price would be and after finding out the price i decided not to get the watch just the phone. Months later I noticed that my bill was extremely high so me and my mom called in to find out and we were told that I was being charged for an apple watch but we told them that we did not get an apple watch. My mom has been going back and forth with the manager and no one is helping us get this resolved. She requested the store security footage to be reviewed and they were supposed to call back and never did. My mom called back and the manager said the video shows the store with us leaving with the watch which is not true . She called customer care and they told her the watch has never been used. To this day I am still being charger with a device I do not have, this is very unfortunate because this is my first bill and I just graduated high school trying to be responsible so I don't want to not just pay my bill. I wish someone could help me resolve this issue but it sounds like no one from t-mobile is willing to help me with this matter. Once my device is paid off Im gonna leave T-mobile because it's not fair how I've been treated. If someone is willing to help or know what I should do please contact my mom @natoushamangum@yahoo.com