"The so called pay as you use account"

I have an account in Nedbank which was current account but I requested to close it due to charges, they convinced me to convect it to a "Pay as you use account" fine all to find out is that I pay while I haven't used. I request closure on the customer care and they said they can't and I have little time to visit the branch because am always at work. I contacted them on Facebook but still they havent close the account. Today they send me a massage saying my account is overdraw, how because i never use the account.