A-to-Z claim, funded by Amazon, and Amazon won't refund our money.

The customer files an A-Z claim, saying they haven't received the product. We prove they have, and they agree with us. The refund is funded by Amazon on February 14th. Well, to date, we haven't received our money. We contacted Seller Support repeatedly, and they told us they would transfer the request to the appropriate department and send us an email with a response. We haven't received a response, and we haven't received the money. I understand this is outright theft. Who should we contact to receive our money?