Telkom *****ing from me. Cant cancel contract.

Telkom came to install fibre which never worked. I had internet problems from the day it was installed. I then tried cancelling my contract in March 2018 which is impossible to do. I have subsequently moved cities and am no longer even living in the house with the line. I have sent multiple requests and called multiple times to follow up on the cancellation of the contract and Telkom still fails to assist me. Telkom continue to bill me and if I dont pay, they add it to my credit record and black list me, therefore forcing me to pay. Telkom is *****ing from me and I dont know what to do anymore!?