Nedbank dont want to close my account

I have a Nedbank cheque account which I no longer need because I now bank with blue bank, the account has positive balance, I went to a branch at fox street to closed the account to my surprise the consulted refuse to close, the tell me there is a debit order on my account which I did no authorised and beside if there is debit order on that account, what is stopping them to closed my account and there worse is the account is dormant and if I deposited money they will blacklist me. I guess is time for me to also close my credit card and move my investments also