Bad service

I requested for my contract to be cancelled in October 2020 as I no longer have the car with the tracking device. My bank account was debited in November and December 2020. I phoned again to find out why the contract has not been cancelled,I was told that it's an error I should not have been debited. I reversed those debit orders. Today (Feb 2021) my account was debited again and I received an invoice showing that my account is overdue with the same debit orders I reversed. It looks like my bank account has turned into a play ground for Mix Telematics. I'm not sure if I still want to use them for my other cars. What comfort can you get in them to secure your car if they are failing with administrative issues like debit orders. I tried to call them for the third time now to deal with the same issue,their lines are busy and I'm using my personal limited airtime .