Netstar ignores request to cancel contract

I have been trying since Feb 2019 to cancel my contract for my motor vehicle tracking device, but without any success. Getting the same response over and over again: "Your request has been escalated to our cancellation department." Meanwhile they keep on deducting the monthly fee from my bank account. I have reversed the debit order payments, but now a Collection Agency, acting on their behalf, is threatening me. Stay far away from Netstar, their service is BAD BAD!