Corporation Bank — refund not processed by corp bank, initiated by amazon

I had ordered some items from amazon of rupees 5336 and amount paid through online, from my corporation bank account on 29 09 2019. But mistakely i made order one same item twice of rupees 349. I found the mistake, the same day i cancelled both the order. Amazon inform me refund will be credited within 2 or 3 days. 4 days after i contact amazon they said that refund initiated on 30th september and gave me the refund reference number (2750 21) and also told me to contact the customer care of corporation bank. I contacted the corp customer care they told me that they have no idea about the refund proceedings. Again i contact with the amazon they give me the same answer, also advise me to contact online complaint forum. Still i haven't received my refund. So i kindly request you to solve this problem as soon as possible.