Amazon - refund of the returned item with amazon

Hi Sir,
We have bought an Apple strap from Amazon(order No - ***-*******-*******) on ** Mar, **** which cost me around Rs **,***. Unfortunately, it was not compatible with my watch. We called customer care and discussed this issue with them. With their help , a return request of the item was raised.
On ** the March ****, amazon delivery agent came to pick up the return item. Agent verified the item infront of us and after successful verification, he took the item with him to deposit it in the amazon warehouse.
We were supposed to get the refund within next *-* working days. Even after waiting for * days , we didn't receive refund. We finally called customer care. Customer care was very unsupportive. He said that because of item mismatch my refund was cancelled and he won't be able to help any more on this.
On your behalf , we want to know from them
*.When are they processing the refund.
*. How this item mismatch happened when this item was successfully verified by the Amazon delivery Agent at the time of return.
*. Amazon is not ready to share the investigation report.
*. Even in case of mismatched item, they are not ready to return the mismatched item back to customer. Basically, they asked me to bear the loss of **k.
*. What was the serial number before and what was the serial number of the returned item.

It is hard earned money of **k. Please help me to get the refund of the returned item from Amazon.

Regards,
Akanxa