Received huge bill for account closed 3 years ago!

I lived in a student house in Stellenbosch in 2012 and had a Telkom like put in under my name. At the end of the year I moved out of the student house and 'closed' the Telkom ADSL line. In December 2015 I received a phone call from collection services wanting money from me. It turns out Telkom never closed my account and has been charging me monthly and sending the account via post to the house that I no longer live at any more. I was unaware of this and they kept the line open even though I was no longer paying them. Now I have a massive account to settle and collection services calling me constantly. I went in to Telkom to resolve the issue but nothing has happened. I don't even know if the line is closed yet. Number: ***