NuDebt bullying tactics to create fear

I cancelled my Telkom line and ADSL in 2018 and paid in full. I had no contract with them. My online presence on Telkom's website was cancelled by them at the same time. NuDebt Management Telkom are harassing me saying I owe Telkom money. I don't. I reply to their emails, which they don't read and they just send another using bullying tactics to try and instil fear.