Customer refused delivery and was refunded

I sell heavy and bulky items which cost a lot to deliver them to the customer, in recent days few of customers simply refused to take the delivery. I did not receive any cancellation request or any message from the customer I only received the email saying the has customer refunded.
In this case I have been charged twice (for delivery and returns) but customer received a full refund, in our return policy we have mentioned clearly that buyer pays for the return in case changed its mind.
Contacted Amazon seller Support and provided them all the evidence and it’s been 7 days; they did not reply with any update.
Is there any option available for a seller to charge the return delivery charges? Thanks