Can't get a simple Debit order to work

I seem to have a different problem to most people here as I can't get Cell C to do a simple debit order off my Credit card. Firstly they get the CCV number wrong or so they said, then they get the expiry date wrong. They then debit you one month then not another. Thanks to Cell C it is affecting my credit score because they keep saying I haven't paid and then I have to do a manual payment. No again this month after two months of the debit order running it hasn't run again and now I must go and sort it out again because of your incompetence. If you don't want me as a customer just say so and I will go somewhere else.