rehabilitated customer being disregarded

I have opened a personal account and business accounts with fnb and have really been maintaining my accounts but I had previously lost my job and that has caused my accounts to go into arrears and eventually be written off. fnb as an institution now does not want to assist me in upgrading my account as they are still talking about the previous accounts I owe money on. I have offered to pay the account buy they say that it has been written off and they are no longer persuing these monies but they will still not assist me in upgrading my new account. how does a business like FNB not assist clients, as a business that claims to support social justice. this is frustrating and I have considered moving all my accounts to another bank but it seems FNB has too many customers therefore they don't care if they lose business. I have been trying for more than 4 months now to have this account upgraded.