Debit note credit note

SIR,

DURING NOVEMBER 2020 WE RECEIVED DEBIT NOTE AS WELL AS CREDIT NOTE MISTAKE ADJUSTED BY THE SELLER FOR 100000    +  9000 +  9000

BUT BY MISTAKE WE DECLARED IN GSTR 1 FOR THAT AMOUNT (i.e we considered that debit not also as purchase and did sales )

BUT THE SAME MONTH THEY ISSUED CREDIT NOTE ALSO FOR THE SAME AMOUNT.

GSTR 4B STILL NOT FILED.

CAN I LESS THE SALES IN 3B AND ALSO CAN AMEND THE NEXT MONTH GSTR 1 B2CS  SIR?