Air India — Refund issue

I have booked my flight from new delhi to washignton iad in june 2023 . In december 2023 i have changed the dates of flight to june 2024 and in may 2024 i have cancelled the flight. As per air india i provided them all the necessary details about account details and everything still they are not giving my refund back .
E ticket no. [protected]
pnr : wgb6or
case id : 06351141, 07955125
refund amount : $1500