Tommy Hilfiger Charged Me Extra for Exchanging Discounted Sneakers at Ankamall Store

I bought men's TH Cupset RWB sneakers, size 42, with a 40% discount on the Tommy Hilfiger website for ₺2,729.40. When the order arrived, I found the shoe too small and wanted to exchange it for a larger size. I went to the Ankara Ankamall store, as they handle returns and exchanges according to the website. At the store, I requested a size larger shoe, and they exchanged it but charged me an additional ₺1,269.60. If I had returned the shoes via cargo, I would have received a larger size for free. Moreover, they issued an informal receipt, which I believe is tax evasion. I am filing a complaint against the store and its staff and demand the unjust extra charge be refunded. If this issue is not resolved, I will pursue all legal remedies.