Telkom account cancellation woes

I sold a company in July 2018 and attempted to cancel my Telkom account for that company in early August 2018. After numerous e-mails, calls and on-line cancellation attempts, I seemed to have got the account cancelled on the on-line platform after about a week of trying. In October 2018 after receiving continuous accounts for the 'cancelled' account for August and September, I called the Telkom help line and after a 20 minute wait was assisted by a telkom employee. The Telkom employee advised me, after 10 minutes of checking on their side, that they had indeed received my cancellation and that there was no outstanding payment due. I received a reference number for this. In the past month, I have now been targeted by Telkom's debt collection 'lawyers', who are extremely rude and do not have any communication s****s. after trying to explain to them the history, they simply tell me that I have to pay 'or else!' I have blocked all their numbers.