Account not closed

I have called the nedbank call center to close the account which I opened last month and a day later requested that the account be closed as I went with another bank.. Late last month someone called me from the call center center and I told her my issue and that I requested that the account be closed she advised that she will get someone to call me to close the account however no one did... I received a letter in the post to go to the back and varify the account.. I don't need to verify the account as I told them to close the account but why was this not done.. And now you are probably going to bill me for something that I am not using. This is really poor service.