Mavi Jeans Return and Exchange Problem

In June, I purchased a pair of Tilda model jeans for my daughter from a Mavi Jeans store. We collected the product from the store, but since we were out of town, we didn’t have the chance to try it on. When we returned to Istanbul, we tried the jeans and realized they did not fit my daughter. Today, I went back to the same store to exchange or return the product, which is completely unused with its tag, packaging, and all accessories intact. However, neither an exchange nor a refund was accepted. Even though we had the receipt, I was not satisfied with the behavior of the store manager or customer service. Now we are left with a product we paid 1,400 ₺ for, and this situation has made me feel really bad. My primary request is a refund, but if that is not possible, I would at least like a gift voucher. I want this issue to be resolved.