Irritated about cancelations not happening

I have sent through my adsl cancelation on the 9th April 2018, I have phoned to follow up 7 times already, and each time i call they tell me they have no notice of cancelation and I need to resend the form to service cancelation and cc the person on the line as they promise to get it sorted out, so I have 7 email address and even a Managers email address who promised to sort this out on Friday! It is still not sorted and I am still being billed monthly for a service that has not been used for months! Telkom you are absolutely useless and I don't know how much more to beg you to cancel my line and refund the amounts that have been billed after cancelation.