Trendyol Charged Me for 500g but Sent 450g and Refused to Process a Refund

I ordered from "Köfteci Yusuf" through Trendyol, and what I received did not match what I paid for. I ordered 500 grams of merchandise, was charged for the entire amount, and received just 450 grams. When I contacted them to request a refund, I was told that they would not accept returns. I found this quite frustrating because Köfteci Yusuf said they were not liable because the order was placed through Trendyol. They advised me to tackle the issue with Trendyol instead. This lack of responsibility and customer service is distressing. I expected more from such a respected brand. It is irresponsible to refuse to accept responsibility for shortchanging a consumer, and both Köfteci Yusuf and Trendyol have disappointed me.