struggling to cancel a contract

I had a vehicle fitted with a chase tracker unit a while ago. I have had multiple issues with them not deducting the premium monthly and letting the contract for into arrears for month at a time before they call and advise you that the contract has not been paid. In November 2017 I advised them that they should cancel the contract. I was advised to pay a cancellation amount as well as the arrears. I called again in December and in January 2018 and I bastion another amount to pay. I them paid the outstanding amount, e-mailed the proof of postage , faced the proof of postage and instructions to cancel. So this morning 05 February 2018, I called to confirm that its cancelleed. The first consultant I spoke to just couldn't help me and put me back to the switch board. I them spoke to someone in billing department and she wants to k ow when I'm going to pay. She's apparently escalated the matter now to see why it's not cancelled.

Beauty of it all is that I sold the said vehicle in January when this was supposed to be cancelled

I'm annoyed