Paid up letter and credit record update

I had an account with FNB and I lost my job in 2012, the account accumulated bank charges over R4000 even though I told them I was unemployed. They handed the account to Nimble group and finally I was able to pay the account a month ago after they gave me a settlement amount. Till this day I've been following up NBA for a paid up letter and they're telling me that they're waiting for FNB to send the letter. They're refusing to give me direct contacts for FNB. I've been frustrated by this account because I don't understand how does an account accumulate so much charges if it's not used but non the less I've paid the settlement NBA gave me. Can I please have the up letter and my credit record updated.