Has it been more than a week since they arrived, because you were away? Their policy allows return/exchange for wrong size within a week.
Customer's Responsibility:
1.Incorrect order(size of the item)
If the customer has ordered an incorrect size or product, we can also allow a return. In this case:
(1)For an exchange, the customer will be responsible for the shipping fee to send us back. we will cover >shipping fees for sending a replacement shoe.
(2) For the refund, the customer will be responsible for the shipping fee to send us back. and we will deduct a >flat Processing Fee of USD 5.00 each pair shoe when we refund money to every client
NOTE: The shoes are only returnable within 7 days of delivery.
What size does it say inside the shoe? They are listed on the website in US sizes, but the shoes are labeled in the European equivalent. So if you ordered 6.5, they should say 37 inside, in the heel. If you are posting them in your local Buy Nothing group on Facebook, you could include that information.
And if you don’t find a taker, you could bring them to the Seattle Eastside Book & Map exchange, which I hope the weather will allow in early May. If they are slip-on style size 37, I might be interested, depending on the color.
In the meantime, Amazon has the slip-on style in size 6 for $23 in some colors, such as light grey.