Ongoing Connectivity Issues with Xiaomi Mi TV Stick 4K - Request for Warranty Support

I purchased a "Xiaomi Mi TV Stick 4K Android TV Media Player" from Amazon on April 24, 2023, and it has a 2-year warranty. Currently, I am experiencing issues connecting to the internet, with frequent disconnections. Due to these problems, I wanted to send the product for service. I reached out to service providers such as Genpa, Evafon, and Ouno for a solution to this issue. They requested the "serial number" of the product.
Since I have had the product for over a year, I could not find the "serial number" on the box. Therefore, I requested this "serial number" from the customer representative on Amazon.com.tr. They informed me that they could not provide this number. I explained that I was asking for this number for a product I purchased from them and that is still under warranty. Otherwise, I stated that I was unable to repair a defective product that is still under warranty.
The service providers told me that the "invoice" for the purchased product must have the serial number and that it needs to be a signed and stamped invoice. When I mentioned this request to the Amazon customer representative, they said they could not assist with this issue.
As a result, I am unable to repair or exchange a defective product that is still under warranty, despite having the invoice. Additionally, the product's price was ₺1,119 last year, but it is currently listed at ₺1,849 on amazon.com.tr. I request that my situation be addressed promptly. Thank you.