WONT STOP CHARGING ME FOR SERVICES NEVER ASKED FOR OR USED

I have been charged for Internet services for over 4 years which I understood to be internet charges, which I had purchased. When I cancelled my internet service due to shocking service and zero connectivity, the charges continued. I made numerous calls to Telkom to ascertain what the charges related to as I had evidence of the cancellation of the Internet. I was sent to the branch office in Fourways and the sales agent said it was for the Telkom "****le". As I had NEVER been given the ****le, I NEVER used the service. I was given a cancellation form and told the matter would be resolved and I would receive a full refund. This was done on 21/03/2017. I send an eMail to Telkom once a week telling them to stop *****ING my money. They do not have any right to keep money that services were not requested or provided. I am my wits-end to get them to stop billing me, (which I pay so I do not have my Land-line disconnected) WHAT ON EARTH CAN I DO NOW. Please help me.