I've reviewed your email and understand that your concern regarding order #104-6100932-2649857. I will assist you with this issue.
I've checked the buyer-seller messages and I see that you the buyer wants refund and you have asked for a proof.
In this case, if you feel that you have shipped the correct item in good condition then you don't need to issue refund to the buyer.
I would like to inform you that, this solution might prompt the buyer file A-Z Guarantee Claim against the order. However, when a claim is filed, Amazon contacts both the parties and take appropriate action. If there is no error from your end, you can always appeal for A to Z guarantee claim and the feedback submitted by the buyer with the appropriate proof. Therefore, I request you not to worry about the outcome of the claim as Amazon gives you a chance to appeal.
Please be assured that when an A-to-z Guarantee claim occur, Amazon.com usually does not hold the seller responsible for the reimbursement of a claim if a seller follows the Amazon.com Community Rules when listing, selling, and shipping their item.
Sometimes, a buyer may also decide to leave negative feedback for a Seller. In this case, if the feedback qualifies for removal, our feedback removal team will remove it. You can contact our feedback removal team by logging into your seller account and choosing the following option from the Contact Us form within the Seller Help section:
Contact Us > Orders > Customer Feedback Problems
Please remember to include the Order ID and an explanation of why you would like the feedback to be reviewed. You will likely receive a response within 24 hours of submitting your request.
I hope this information helps. We greatly appreciate your understanding in this regard.
Thank you for being a part of Amazon.