FNB must fall

On the 24 July 2018 I settled my Fnb revolving account and got the paid up letter but now ,the account is still open and interest is being added on the account . I call and get transferred from pillar to post with no assistance on closing the account and to get my name cleared from ITC/credit berue. my frustration is that 2 accounts from fnb were settled same day but only 1 account was updated and closed I can see it on my credit report but the other one is still outstanding and showing me that I owe FNB R13520 also on my fnb app the account is still not closed. Can some one who knows their job and assist me to sort this issue and clear my name