Telkom account handed over for Debt Collection

I cancelled and suspended my Telkom line with immediate effect on the 26 June 2015. I have send numerous emails and made call after call with no reply from Telkom. The new tenants of the premises is using the line on my expense. And Telkom does nothing. A lady eventually called me from Telkom in October 2015 to apologise for the late reply to my cancellation and said she would make sure everything will be rectified. The next thing on the 19 January 2016 without any warning from Telkom a Debt collector contacts me to say that Telkom has handed me over for not paying my account!!! Now I am blacklisted!!! Something I can't afford as I am in business and won't be able to get any new contracts. That meaning there will be job losses in my company. I made call after call from monday to Telkom they just say that they are sorry but the matter is given to the attorneys and I should contact Telkom legal department, they just said to contact the Attorneys handling the case and they say I must contact Telkom. Now what must I do to fix the problem?? As nobody is willing to assist you with the problem they created.