Refusing to closed the credit card account

Over a month ago I fully paid my credit card and requested for the account to be closed. I called them several times asking them to close it, they just said okay it will take few days to close. I then requested a Ref number the lady just said they will send me a paid up letter they won't give any reference number. After a few calls days later one lady was able to send me a reference number but till this day nedbank hasn't closed my account.