Punjab National Bank [PNB] — complaint against refund

Address:

110080

I purchased redmi note 5 mobile phone ₹10299 from amazon on 30/12/2018 and done full payment by debit card and i received but order was returned due to some technical issues on 8/01/2019 and now amazon is saying that refund has been send to bank. So contact customer service and file charge dispute they had given me a no. Refund reference# 75503729009026056222114..
But customer service is saying they can file nothing like charge dispute and can only check if money came to your account or not.
Same behaviour by branch also.
Don't know what to do