Unsatisfactory service

Late last i had an issue with Netstar where they were claiming that i have their tracker installed on my new car, after months of back and forth conversations with them. Netstar after months they finally figured that they were referring to my old vehicle, this took months to sort out and resulted in them handing my account over to their attorneys. I agreed and requested settlement, i settled the account and asked them cancel it this in May this year. June, July and August passed after settling that account, September Netstar started debiting my account, i phoned and enquires why are they debiting me again. They claimed i have their services i explained that an account i had with them was settled and cancelled, i forwarded the correspondence to them but i have received no help. Instead of them looking into the matter they handed my account to their collectors. I have had 100s conversations with collections agent, and i have repeatedly explained the situation. Day in day out i am asked to send correspondences to them to assist, but still this matter has not been resolved. Yesterday i got a call again from an agent from Netstar who was rude and refused to listen to my side of the story, she said she is not interested in my story but only in what she sees in front of her, from September until now i received calls which clearly indicated that the system they used is flawed, cause the matter has not been looked because after all the million calls i have been receiving, none of them assists. The person who called said they will continue you to pester will calls, cause theres nothing they can do, but only expect a payment from me and to her in seems the cancellation was not successful. I asked how do i pay for services i have been telling them that i do not have as the account should have been cancelled in my. All correspondences they have, and email sent to their accounts department requesting this matter to be escalated and looked into. However to this date none of the people i have been talking to helped.