Samsung Service Has Ruined My Phone, and I Require a Replacement

I'm writing to express my dissatisfaction with the phone service for the Teknosa device I purchased. Teknosa arranged for the phone to be delivered to the service center. On August 19th, I was notified that the procedures had been completed, the tests had been successful, and the device had been handed over to the courier. There is a Teknosa delivery receipt, and the courier delivered it on August 22nd. Throughout this time, I've been wondering how the courier can ensure that my phone's parts haven't been tampered with or replaced. They cited a "system error" as the reason for the lack of changes. I noticed a gap between the back cover and the device as soon as I received it. The power button, in particular, does not work smoothly and is slightly depressed. When I sent the device in for repair, there was no external damage, not even a scratch, according to my records. As a replacement, I insist on a new device. I'd like to emphasize that I'm not going to let this go and will take legal action if necessary. I returned the device to you via courier today. In exchange, I expect a new device. Please be aware that I am determined to see this through to a satisfactory conclusion.