Trendyol Rejects Return of Defective TP-Link Modem

I purchased a TP-Link TD-W9960 modem in Kurtalan, Siirt, and starting from around 21–27 December I noticed that the device is very slow, has a very weak performance and gets excessively hot during use. The modem does not provide a stable and sufficient internet experience and the overheating worries me in terms of both performance and safety. In addition, the packaging was very poor and low quality, and the product reached me in an open and used condition, which clearly shows that it was not delivered as a new and properly packaged device. Because of these problems I contacted Trendyol customer service and the seller and stated that I wanted to return the product. However, I was informed that my return request was rejected and that they would not accept the device back despite the clearly problematic condition of the modem. I request that the sale of this defective TP-Link TD-W9960 be cancelled and that the full amount I paid be refunded to me as soon as possible.