Telkom not cancelling ADSL since November 2017

I am trying since November 2017 to have my Telkom ADSL line cancelled. I went to the Potchefstroom branch, the lady assured me that the line will be cancelled on the date specified. Since then I have been attempting to get my deposit back from them with no success. Numerous calls and emails have been made to the cancellation department and I still get invoiced every month.