Trendyol Product Return Rejection

On August 19, 2025, I ordered "An Introduction to Quantum Physics" from the seller Uyksuz Kitap through Trendyol. The next day, I realized I had purchased the wrong book and returned it, packaging it undamaged, using the "I chose the wrong product" option in the Trendyol app. However, on August 27, 2025, the seller rejected my return request, claiming the product was not for resale. I contacted Trendyol customer service via live chat. They said they would investigate and resolve the issue, but I haven't received any positive results yet. The product will be sent back to me, but I don't want to purchase the wrong product; I request a refund. I paid ₺525 by credit card. I also requested an invoice, which I was told would be emailed to me within 7 days. Because I've experienced similar issues before, I sought a solution through Trendyol instead of contacting the seller directly. I no longer trust the seller and am wasting my time in this process. I request a refund as soon as possible. Otherwise, I would like to state that I will use my legal rights and share the situation on social media.