Deichmann Refuses to Exchange Defective Boot Bought in Promotion

I purchased a pair of women’s boots from Deichmann at Edirne Margi Outlet on 25.12.2025 within the “buy 2 pay 1” campaign. While trying the boots at home, I noticed a large burn mark that I had not seen in the store at the time of purchase. I went back to the store and reported that only one of the boots was damaged and asked to exchange just this damaged boot. However, the store staff told me that because the product was bought as part of a campaign, they could only exchange both pairs together and refused to change only the defective boot. I like the other pair of shoes I bought and do not want to return or exchange them, as there is no problem with that one. I only want the defective, burnt boot to be exchanged with a fault-free one under my consumer rights. I kindly request that Deichmann allow the exchange of only the damaged boot and resolve this situation in my favor as soon as possible.