Disparities in Product Shade and Extra Fees at GAP

I purchased the product with the code number 321894110 from the GAP store. During the purchase, I informed the staff that I wanted the product in white. Instead, the employee offered me a different color for a special promotion. Later, they promised me that I could easily exchange this shade for white. When I tried to exchange the product for a white one a few days later, they suddenly demanded an additional fee of 400 ₺. Initially, they assured me that a direct exchange was possible, only to then, in order to complete the sale, suddenly and without warning, demand this additional fee. While they did allow the exchange after the purchase, they insisted on charging extra fees for it. Despite multiple visits to the store to proceed with the exchange, they refused to provide any assistance and attempted to dismiss my concerns.