Bad customer service and order takes long

The order took an extended period to arrive, and upon arrival, the shoes were the wrong size. Despite my order for a size 4 (37), as specified on their website, they delivered a size 3. When I informed them of the discrepancy, clarifying that I had requested a size 4 (37), they insisted I cover the delivery costs to return the shoes. However, the error originated from their end. When I presented evidence of my size 4 (37) order versus their delivery of size 3, they attributed it to a misunderstanding regarding US sizing. Even if the shoes were labeled in US sizes, the responsibility for this oversight lies with their team. It is common knowledge that a size UK 4 (EU 37) corresponds to a US 6.5/7, not a US 4/3. Despite this, they maintain that I must incur the return delivery expenses due to my alleged mistake in ordering the "wrong size." This logic appears flawed