MTN - Very poor service

I took out a new contract last year September for my daughter. The number I received was a refurbished number as I keep receiving SMS's for a Phakile from different accounts holders. I keep getting billed for about 17GB of data used over and above the amount I receive. I have switched off all reoccurring data, sms and airtime on my number. So, how can I be billed for that data used. They are also charging me for self service purchases which is impossible as I purchase data via my banking app. I have been to the MTN store on two separate months but haven't had any joy. If you phone customer care they tell you to go to a store. If you go to a store they log a complaint and tell you to contact customer care. And so you run from pillar to post and no one can help you with your problem.