21 Days Notice for a Sold Car after contract lapsed

Called Cartrack before selling my car and was told that there is no need to transfer the tracker to the new car that I will get on 4 March 2025 as the contract is coming to an end. No need to cancel either. I then sold my car on 26 Feb 2025. Month end I got a bill for the sold car and seeing the new tracker was installed on 6 March 2025 I now have a bill of R619.69 for 3 cars of which 1 no longer belongs to me. I tried speaking to the customer care but she does not understand and insist that I need to give 21 days notice. This is not aligned to how the insurance houses work. I would need to go to the Consumer Tribunal and will seek compensation for the pain, distress and suffering experienced