********** contract

So a month ago Cell C debited my account out of the blue, and naturally I assumed it was just a mistake and disputed the debit. Yesterday they debited my account again, and again I disputed the debit, then I get a call from cell c claiming I have a contract with them, which is surprising to me considering I haven't been in contact with any mobile service providers this year. Then the rude lady shouts at me and hangs up. Should I open a ***** case against Cell C? What exactly are my options here?