Hellkom, billing for services never asked for

A while ago I entered into a line-rental agreement with Telkom. The agreement was for a landline only, as I wanted to use it for the internet, and nothing else. Shortly after, I noticed that I am being charged R150 more than line rental only and then my frustration started. After calling them to find out what the reason for this charge was, which was voice line rental, I repeatedly told the consultant that I DO NOT want or need line rental. I still have my first bill from October 2017 which shows nothing about voice line rental. These consultants promised to remove this charge but month by month they send this charge through. Even when I cancel the payment at the bank they send it double through the next month. It defies logic how a company can just take your money without your permission, and a government parastatal at that. The Telkom consultants are largely ******** when it comes to paying your money back. Is there some kind of watchdog body with teeth who can get Telkom to comply? I can't wait to get fibre and get rid once and for all of Hellkom!