Balance on credit card acct

I received a registered letter regarding my FNB credit card account, demanding payment for account ***18 7000, from Groenewald and Lubbe. In May 2009 FNB proposed to my debt counsellor that the balance of R28606.46 be paid over 60 months @ 15.00% translating into an instalment of R680,54 per month. Payments were made to this arrangement from 2009 onwards, which means the account was settled last year, and showed as such on PDA statement. <br> <br> On 26/03/2012 the verified balance on court order amounts to R21 528.56, FNB now however claims that my balance at that stage was R48 042,65 on 26/03/2012. To date no one could give me an answer as to how they arrived at this balance. This balance(R48042,65), was not verified at any stage or on any documentation. Also the address they supposedly have on the statement is not my place of residence. I think somewhere a grave accounting error or capturing error was made.<br> <br> Your urgent attention is required in this matter. <br>