FIRST NATIONAL BANK - WHY DID YOU RELEASE THE TITLE DEEDS IF THE BOND HAD NOT BEEN CLEARED??????

I sold my property last year in October. The bond was settled and I moved on with my life. Now I receive a demanding letter from FIRST NATIONAL BANK HOME LOANS RESIDUAL COLLECTIONS to say that I owe them R24,324.30 I have tried phoning *** Boithatelo Judith Mokoena the person that sent me the email. HOW DO YOU RELEASE THE TITLE DEEDS TO THE PROPERTY IF THE BOND HAS NOT BEEN SETTLED IN FULL. !!!!!!