Unable to cancel contracts

I have 4 contracts with Vodacom, 2 of which contracts has come to the end of their term already. I have called many times to have these contracts changed to pay as you go accounts but every month they just keep deducting for the 4 contracts. I have even mailed their complaints department but they do not reply. When I called the cancellations department 2 month ago they promised to fix this and refund me this however also did not happen. When I call the cancellation department they refer me to the collections department and vice versa. No one assists. I have reversed the last 2 debit orders in the hope that Vodacom will contact me and fix this mess.