Telkom useless - How do you cancel your line

Telkom hasn't responded to my cancellation of my telkom line - I've paid until July 2018. Thereafter once again tried cancellation process, been on the phone with a few people from Telkom who then helped me with the process online. Still I am receiving a bill every month.

How difficult can it be to get rid of the them!! Also I've actually never gotten to use my telkom line because they took too long with the installation, I just haven't been able to cancel it.