Unable to cancell mix telematics contract

I cancelled my 2 trackers and paid the early cancellation fee in June last year (2025) because I sold my Hilux. After numerous phone calls and emails I am still being charged a monthly fee by debit order. I see on the ratings this is a common problem with Mix Telematics customer service. I tried my best to remedy but they were unable to correct this. They owe me allmost a years fees on 2 trackers.