Amazon India — Wrong item received and refusing to refund

Address:

Brigade Gateway, 8th floor, 26/1, Dr. Rajkumar Road, Malleshwaram. Bangalore.

I ordered a iPhone 13 pro back cover through amazon on 16th July, 2022 for Rs. 1699. I received a wrong product against this. I received a iPhone 8Plus back cover. Immediately after receiving the product I complaint against the same and shared images of the wrong item. I called the customer service and she checked thoroughly all the details and she herself helped me with raising a refund against the wrong item and told me that I will get a refund of Rs. 1699 once the product reaches them.
The wrong item was picked up from my home on the 22nd July, 2022. But still there has been no refund on my account. Infact in the Amazon app it is showing since the last 4days that the product is in the way back to amazon. It is when I called the customer service yesterday I came to know that there is some investigation going for my issue and I will get a update in the next 3days.
I received a mail yesterday night from amazon stating that at the time of dispatching the order from their fulfilment centre the product was correct and the item which I sent back to them is incorrect so I am not eligible for a refund. I called the customer care today morning and they told me the same thing, I asked them that where is their fulfilment centre as it may have happened that after leaving from the fulfilment centre the product may be changed but they didn't answer to my question. They just told me that I am not eligible for refund and disconnected the call.
I even mailed them for this but in vain.

SO HEREBY I WANT TO REQUEST THE FORUM TO KINDLY HELP ME IN GETTING MY MONEY AGAINST A WRONG PRODUCT.

I am not able to share images of the Wong product as I have already sent it back to amazon. I am attaching the invoice and mails.