Trendyol Did Not Send the Honor Pen That Was Promised With My Pad X9A Tablet

I ordered a Honor Pad X9A tablet from Trendyol with order number 10135388361. During the sale, it was clearly stated that an Honor brand tablet pen would be included, and the pen is even listed on the invoice. However, the pen was never sent. I waited several days thinking it might be shipped separately, but nothing arrived. When I call Trendyol, they tell me to contact the seller, and when I call Honor Türkiye, they say it's not their responsibility. I also messaged through the Trendyol app, but received only generic responses with no real help. I’m completely lost on what to do. Neither Honor nor Trendyol has offered any solution.