Bad Standing status

Hello, i bank with FNB, having come back after leaving for a few years. i have been trying to get vehicle finance so i could retain my job, as its a requirement, from dealers and have been declined due to a "bad standing" status that FNB has me on for outstanding bank charges that they had subsequently written off, it wasnt a loan or over draft or anything where i had borrowed. i had called FNB a year ago requesting to pay back this money that i owed them but was told i cant pay back the money cos its been written off. i have a good credit record but i cant get finance. i am willing to pay back the money FNB wrote off as i need the bad standing taken off but the bank is refusing. i bank with them and my salary goes in there but they are not willing to help. all other banks wont consider me now for finance because of a debt im not even allowed to pay back. i need my status updated so i can retain my job and be able to work for my kids. please help me.