I regret taking cell c contract

As a young professional who was looking for great data bundles deal, I agreed to a 24 months contract with cell c. The biggest mistake of my life. Upon the expiry of the contract, I called countless times to try to cancel the contract, they sent me from pillar to post. Finally I managed to cancel it, guess what, their accounts department continued to debit my account irregardless of the contract being canceled, actually, the accounts department doubled the invoice from R249 to R600+. At the end of the day. They messed up my credit record which is what happens when you refuse to extend their contract. This explains why they are where they are today in terms of business