Telkom does not wnat to cancel my account

It has now been more than a year that I have tried to cancel my companies TI-AllAccess Advanced 20GB account from telkom. They just keep redirecting my calls and never respond to any of my cancellation emails. This is really unacceptable as i have to put in a debit order stop every three months and it never seems to stick. Can someone please advise with what can be done regarding this because paying every month for a service that has not been used in 3 years is ludicrous.