Vodacom contract

Good day, I am having the worst experience with Vodacom and they are taking my money and I'm unable to do anything about it. I currently have 2 data contracts which i have cancelled, but they have not cancelled and is debiting my account. They have sold me a data contract which does not exist. I have contacted the after sales department and spoke to 2 agents. They advised me that it's canceled, but it was lies. Everytime I call them, I get no assistance. I even went to an outlet, and they told me they cannot help me because I took the contract over the phone. Please help me, my money is being debited out of my account every month. And I can't reverse it because it's more than R500.