Contract cancellation

Telkom is still billing me for a contract that expired and was cancelled last year in October. I have called the customer service centre numerous times but NOTHING HAS BEEN DONE!!! This is unacceptable. Why Im I being billed for a contract that Ive cancelled? No one in Telkom wants to explain anything. This is totally unacceptable and I would NOT AT ALL RECOMMEND ANYONE TO TAKE ANY CONTRACT WITH TELKOM.