Lenovo Legion 5 Keeps Freezing and Shutting Down

I purchased a Lenovo Legion 5 laptop through Vatan Bilgisayar in three installments for approximately $2,610. About a week after receiving the device, it started freezing and shutting down on its own repeatedly, so I sent it to an authorized Lenovo service center with an explicit request for a refund on the grounds that the product was defective.
Despite sending the device in with a clearly stated refund request, about a month later it was returned to me — with the service form indicating that a motherboard repair had been performed. Even though I had explicitly exercised my right to a refund, my consumer choice was completely disregarded and the device was repaired and sent back to me instead.
On top of all that, the freezing and spontaneous shutdown problem is still happening after everything. Despite trying to reach Lenovo customer service by phone numerous times, my calls were never even answered, and no solution or follow-up of any kind was provided. This entire process has left me deeply wronged and has completely destroyed whatever trust I had in the brand.
I'm demanding that my refund request for this defective product be honored, that the harm I've suffered be remedied, and that my legal consumer rights be properly applied. I want to make clear that if this is not resolved, I am fully prepared to continue with the legal proceedings I have already initiated.