GSTR-2A Shows 3B not filed but actually files

Being a QRMP scheme GST filer, i've filed GSTR-3B for the period oct-23 in the month of Jan-24, but my customer says that while viewing his Oct Gstr-2a in Dec-24 also, it displays  GSTR-3B filing status as No. But ive filed my GSTR-3B in Jan-24 itself..despite providing all proofs for filing 3B in Jan-24 by Gst portal return status and submitted 3b copy also. He still sticks to Gstr-2a and deducted GST amount. How is it possible that GSTR-2A shows filing as N despite 3b filed. How to prove that 3B is filed.