Dual-Monitor PC Not Working - No Replacement

I purchased a dual-monitor computer from the seller Atom Bilişim on Trendyol. When the product arrived, the required DVI converter needed to use the computer with two monitors was missing from the box. I immediately tried to contact the seller via Trendyol, phone, and WhatsApp, but I received almost no proper response or assistance. I had to use the computer with a single monitor for about two weeks without the converter. After those two weeks, the computer stopped turning on completely, and I was told the issue was caused by the case. Since I couldn’t reach anyone, I also reported the situation through Xolvie. After that, the company asked me to send the product back for repair, but I refused because I wanted a replacement, not a repair, for a device that failed so quickly. No refund was issued, and I have been unable to use this computer for nearly a year. The problem first occurred on December 25, 2024, and it still has not been resolved. My Trendyol order number for this purchase is 9875319374. For a product that malfunctioned in such a short time and has been unusable for so long, I am requesting a replacement with a brand-new, fault-free unit instead of a repair.