Cell C are ******

I had a contract with Cell C and didn't when it was ending but they started calling me to upgrade and told them I won't because I've nothing but bad experience with them. They would call everyday and u would tell them no, when the contract ends I won't be continuing with them. Eventually the contract did end but they continued sending data. The first month it happened I told them to stop over the phone. Second month I write to cellc and tell them to stop sending data I don't want to continue with them. When I inquired about what's happening they told me I'm on a month to month. I was previously paying R299 now it's R645. On twitter the consultant I spoke with said my calls have been logged in as payment disputes and not to actually cancel the contract.