Missing Refund After Banggood Canceled My Order

I placed an order with Banggood (Order #113957450) for ₺9,458.47 and chose the installment option, paying a total of ₺9,972.12 with the interest included. The order was canceled because the product was out of stock, but I was only refunded ₺9,458.47, leaving ₺514 unreturned. I contacted my bank, and they told me the installment plan was through Banggood, so I had to follow up with the company. Banggood customer service claims they refunded the full amount and refuse to cover the installment interest. Why list a product that isn't in stock, take payment, and then not fully refund the amount paid? This feels like a deliberate attempt to profit. I’m down ₺500, and others should be cautious when ordering from this company.