Punjab National Bank [PNB] — transaction dispute pnb

Punjab national bank [pnb] — charge dispute

I purchased coat of ₹779 (₹ 25+ 774) from amazon on 02.01.2019 and done full payment by debit card of 774 but order was returned on next day after the delivery on date 6.01.1996 and now amazon is saying that refund has been sent to your bank so contact customer service and file charge dispute. They had given to me reference number[protected] but customer service is saying that they can file nothing file charge dispute and can only check if money came to your account or not. Same behavior by branch also.
Now don't know what to do.