Stop taking my money!

When I bought my vehicle during October I signed the acceptance to join car track. I cancelled this 3 days later and since then I have been receiving calls non stop for over a 6 weeks now. They debited me at the beginning of November and i reveresed the debit order. In the middle of December they debited me another amount which is not even the installment. Again today I have been debited 2 amounts!! How can you take a debit order for an amount that I did not sign for?? This is *****. I have answered several phone calls and have told numerous staff members that I camcelled and to pleaae calling me. Each one promises they will make a note. Stop taking money from my bank account!! Stop calling me to say I am behind with payments!! I do not want your service. Should I be debited again, I will be taking this further as talking does not help. Do not do business with this company.