Telkom/ NuDebt billing

Good day

I cancelled my Telkom service more than a year ago, Telkom kept billing me and then they decide to use NuDebt to do there work. NuDebt has been emailing me regarding this issue. I explained to NuDebt that my Telkom account has been cancelled more than a year ago. Telkom excuse to them was a dispute was logged and was rejected as they credit the account already, the reason for the credit is because Telkom kept billing me instead of cancelling the account therefore they had to credit. Please sort this out as I cannot continue with these unnecessary emails from NuDebt and Telkom all the time.