Telekom are failing to stop my contract..

I cancelled my contract over a year ago, which had expired. I went into the Greenstone branch and did all the paperwork. The contract was never cancelled and they kept debiting my account. I complained on Hello Peter and some dude from Telkom called me and promised me that they will allocate my matter to someone who'll contact me. This never happened and to this date I'm still getting billed and debited.