TOTAL INCOMPETENCY

In 2002 or 2003 I bought an apartment and sold it 2 years later (i.e. 2004 or 2005). Accordingly the bond was settled and to my knowledge cancelled (Everything was handled by Standard Bank lawyers). Suddenly in 2010 I receive a statement saying I owe them +/- R350 in interest (which by the way was accrued on a 0 balance) after numerous e-mails, calls and finally escalating the matter, I never heard from them again. Until recently. Now suddenly I owe them over R800 which I assume is still interest on a O balance which defies logic. Nobody can explain how interest is calculated on a zero balance and all they keep telling me is that the bond is not cancelled. The e-mails sent in 2010 (thank goodness I kept them) clearly state that any so called money owed must be written off and the bond must be cancelled. I have againe-mailed them withall copies of previous correspondence but I sincerely doubt anything will be done.