Bad service

I have an account with them December they did not deduct or debit my account. January they called and said they going to double deduct I asked why? They said because I owe December. I asked did you try to debit? Because I didn't receive anything from the bank telling me about unsuccessful debit. Then we agreed that they must double deduct. Again they failed. I called them earlier this month asking them why they didn't deduct. The lady who was helping me said my account it's up to date. I said no please double check she said "I'm sure the payment was successfull. I received an sms stating that I failed to pay as promised so l must call the number provided to make an arrangement. Indeed I called the lady told me that my account it's handed over to them they are attorneys. I call Cell C again the lady said they have a problem on their side they are failing to deduct in some of customers accounts so I must pay via EFT or go to the shop to make payment. I asked why are they suspending my line when they know very well that they have a problem, why are they handing me over as if I ran away. She said sorry. I feel like they are denting my name to credit bureau. This is the worst service I've ever received.