Netstar is trying to rob me

Netstar have been debiting my bank account without my consent and now have sent 3 debt collectors after me in the past 6 months.

I had a tracking device in my car through my insurance company that was fitted by Netstart. my premiums were paid through my insurance company. When I changed my car I called Netstar and asked them to move my device to which I was adviced that it would be better to buy a new device from them because the removal would cost the same as fitting a new one and there would be no change to my contract terms. soon after Netstar started debiting me directly whilst they were also still receiving money from my insurer. I contacted them to try sort this issue and after long and angry e-mails they finally agreed and because they had double billed me, the new device was free. From then I also received a refund from them. 3 months after the incident Netstar started trying to debit my bank account for premiums again and I had to keep reversing these as my premiums were paid through my insurer. End of August I moved to a new insurer and Netstart sent me a message informing me they would collect directly from my account to which I agreed. End of September no collection took place and the first week of October I received an e-mail from a debt collection agency telling me my account has been handed over and to my absolute suprise, Netstar had managed to sneak in the three months from last year which they had *******ly tried to debit from my account and I had reversed. I called them on 11 October and they promised to call me back as the individual dealing with my account was still busy. I am still waiting for that call back. I have also sent an e-mail to their complaints department and has received no feedback from them. Their customer service is very bad and if someone knows where I can lodge an official complaint on them, please assist.,