Reckless interest charged !

6 years ago I went under debt review, my FNB Cheque account, overdraft and credit card was suspended and my account marked as dormant by FNB and I had zero access to any of it. FNB were naturally part of the monthly payment distribution and in Feb 2015 the outstanding balance on the overdraft account was paid up in full. FNB however, never closed my suspended overdraft account upon full payment as they should have. Now, 4 months ago when I'm finally out of debt review FNB want payment on 2.5 years of interest charged to a suspended, dormant overdraft account that hasn't seen a single transaction in over 5 years. FNB sent me ZERO correspondence notifying me that even though the account is paid up its still open accruing interest (even though the account is still suspended and I cannot use it). After countless phone calls and e-mails sent, showing detailed statements of all the payments and when the account was paid up, they still refuse to do anything about it and are now ignoring all attempts by myself or my debt counselor.