Punjab National Bank [PNB] — never received refund from online purchase

I purchased product of 2158 inr. From amazon paid 929rs from pay balance and remaining amount of 1229rs with my pnb debit card, and later i returned the product due to unsatisfactory result. On 25 august 2017 the refund was initiated and i got the amount of 929rs which i paid through pay balance on the same day of initiation, but i didn't get remaining amount which i paid through pnb debit card, it's been 18 days now. I complained about the refund to amazon and they said they have sent the refund to the bank and provided me a "refund reference no.[protected]" to contact customer service and file charge dispute.
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.