Amazon India — dispute transaction, refund never processed

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Anand, Gujarat, 388120

Hello,
I requested for refund after returning one product to amazon. Amazon representative said that they have refunded amount on 26th september 2017. But i didn't get yet in my bank account. I went to bank directlyand they checked my account details but this refund has never been processed. So how can i get my amount. Amazon also mentioned me reference number of transaction and i asked to my bank for it but there is no such transaction in my account.. This is the first bad experience for too long refund time with amazon. Hope i will get my amount as soon as possible.
Thank you.