Multiple efforts to Cancel Contract but still getting billed!

I have been trying to cancel my contract since December 2020 30 day notice from when it is supposed to end which was January 2021, but to this day April 15th 2021 I am still being charged for a contract I don't have. I have called multiple times since, and everytime I call I get told they will log a call on all the additional payments I have made and cancel my contract, but I receive nothing. No confirmation sms to tell me its cancelled, Nothing, What is the route that needs to be taken here ?? How am I being held hostage in a contract that I have already finished,? It seems like vodacom does not honour their contracts!