Tracker has become disastrous

In October 2023 I sold my car and cancelled my contract with Tracker. They advised me to pay cancellation fee which I did immediately. They have sent me a confirmation of cancellation letter. Ever since then, Tracker has been: 1. Tracking the sold car and reporting to me about its movement, 2. Attempting to deduct monthly installment for a cancelled contract, 3. Threatening me about non-payment as I dispute every deduction they make. I suspect Tracker is going down the drain. Almost a year down the line, Tracker fails to figure out how to record and respond to my termination transaction. I have reported and complained about this to Tracker so many times and now don't know what to do.