Tracker *****s my money after settlement is paid

I sold my car in August and cancelled my tracker agreement immediately. The call centre gave me a reference to use when I paid my settlment amount. I paid in my settlment amount on the 14th of October. I was debited again on the 1st of November. I phoned the call centre and they said they would sort out the problem that I was given the wrong reference number and they had given me the reference of a previous car that I owned 10 years ago. I explained the situation and they promised they would sort it out. They billed me again on the 1st of December. I am horrified that firstly when I called to cancel my tracker that they could not trace my car because my ID number was apparently wrong and then they give me a reference on a car that I owned 10 years ago. Would I choose this company to protect my valuable asset again? Never!!!! I want my refund back immediately. This is a disgrace. I am being billed for a car that I sold 3 months ago.