Worst network and service provider to have contract with better prepaid

Had a data contract with Vodacom,it expired and wanted to upgrade to home WiFi, went to Vodacom store was advised to call and cancel, and when I did service was awful, tried calling them the entire day till finally my contract got cancelled however they still continued to bill me for data I don't even receive anymore, they continued to debit over R300 for many more months till I decided to dispute the debit at my bank, and now they have marked me as bad payer really? Now I want all the money back debited previous months when contract was cancelled