TELKOM WILL NOT CANCEL MY LANDLINE!!!!!!

I have unsuccessfully tried to cancel my Telkom landline numerous times online, at a Telkom customer service centre (where I was advised they no longer do cancellations) and telephonically on 10210. I have been given an incident & dispute reference but get told today that I need to cancel online!!!!! When I try to do this, it tells me the request to cancel has already been logged. I am STILL being billed for this line rental when I first cancelled in April 2016 and have had no calls on this line since about February 2016!!!!! Does anyone have any advice on how I can solve this issue?