Faulty unit installed

In July I had a unit installed that would be linked to king price insurance, i then received sms's that the device was faulty both from cartrack and king price. In September i send a request for the unit ro be removed since nobody bothered to test or fix the unit meanwhile the debit orders were going off monthly. It's been 5 months and I've been paying for a faulty tracking device. Last week I stopped paying the device because I want the contract terminated as previously requested . An agent called from the fleet department asking what the problem was I explained the situation to her and she informed me that she will escalate the matter to the relevant department manager for them to cancel the contract. Now the collection department is harrasing me for payment. I also asked for a report showing vehicle movements but still haven't received. I cannot be paying for something I'm not using...