Incorrect billing with NO reply from Telkom

Please help!!!<br> I cancelled my line in December 2015 and to date have not received ANY communication from Telkom.<br> In fact they have continued to bill me and now have sent me to a collection agency.<br> They bluntly refuse to allow me to open a dispute.<br> <br> I am highly disappointed as I have not had an issue in the 10 odd years and now I am being treated like this.<br> I am willing to settle account as soon as the correct invoice has been shared just to get them out of my life.