Extremely bad service from cancellations

I sold my car recently and requested a cancellation via email as per the call I had made to them. After a few weeks I received a reply stating that "As discussed telephonically" that the contract is still valid until 2022 and cannot be cancelled. But I never received that call that they were referring to. I therefore phoned the cancellations department and asked them to verify that there was a log stating that they had called me, since their phone calls are recorded and to provide the transcript of the recorded conversation with me. I am still waiting. Surely they could give me the option to continue paying monthly or pay a cancellation fee. I have recently bought a new car and obviously MiX Telematics Africa do not want more business from their existing customers. I proceeded to request a new customer product and received a call within 2 hours, plus it was after business hours. This shows you that MiX Telematics Africa just don't have any after sales support!