B2b transaction reported under nilrate

WE HAVE FILED THE GSTR-1 AFTER 4 OR 5 MONTHS WE IDENTIFIED THAT THE TRANSACTION FILED UNDER NIL RATE IS TAXABLE SO WE HAVE ADDED THE SAME IN GSTR-3B AND PAID THE GST.  NOW HOW TO RECTIFY THE SAME SO THAT IT WILL APPEAR IN GSTR-2A