Nudebt Management is tarnishing my credit score

They are currently managing my Cell C Accounts, and every time I contact them their emails do not exist, and or their number is not answered. I have been asking for an updated statement of account so that I can see how much is outstanding, and to date still haven't received the statement. They debit my account twice a month on dates that we didn't agree for the debit. and they continuously send me a letter of demand, even when they are debiting my account.

They don't know what is happening with their accounts, and they like harassing their clients. even to date, I haven't received any communication as to why they send me a letter of demand when they debit my account monthly, and why they debit my account twice monthly.