Cell C claiming I owe tham while I never had an account with them

Last year I wrote a complain about Cell C *******ly debiting my bank account and they promise to rectify this. I assume they will but I then blocked them for furthering their ******* activities. I recently realized that they are saying I am owing approximately R5000 this is after I told them that I never had an account with them and I'll never. I don't use their services but they have the guts to putting my name on credit bureau to make me look bad. I never wanted to be associated with them. You try to call their legal department, you hold for more 10 minutes, appalling service. I just need to clear my name with this