Harrassed for payment after account cancellation

My business, CV Makeovers, had a Telkom landline and I was listed in yellow and white page directories via Trudon. I cancelled my Telkom account in March 2017 and advised Trudon that I no longer wish to be listed in the directories, as I am relocating to Cape Town and no longer have a Telkom number. They continually send me accounts despite my repeated responses to explain the above. Today they sent me an email threatening to blacklist me! This is harassment and ******* blacklisting.