Cartrack nightmare

I bought last year a car, the place were we bought the car informed us that we have a car tracking system in form cartrack in, but it is for a year free , after a year Cartrack will contact us and confirm if we want to continue with there service and what the amount will be each month if we want to continue with there service. On the 31 October i just woke up and there were a debit order form car track, where did they get my banking details and were did i sign any contract with them, i reversed and deputed the debit order, cartrack's people have been contacting me ever since then after were i informed them it is ***** to just put a debit order on someones account without my consent, i told them i will not pay a cent to them due to i have no contract and no one contacted us to inform us that the year's free cartrack service have expired , it was only then they informed me the dealership have paid it for a year for us and now we must pay, but still i did not sign any agreement to Cartrack for any monthly installments to be deducted form my account !!!!!!! I have then spoke to a agent and they cancelled the cartrack and every day i still get called about the cartrack i have informed the agents i will no longer speak to them and block all there numbers as i will not pay a cent and still they are harassing me every day!!! Bad service and worst company , if i ever buy a new car and i will be informed the car have a tracking system in i will tell them to remove it immediately!