Samsung M31S Smartphone Endless Power Issues and Bad Service Experience

My Samsung M31S phone kept shutting down and starting back up at an alarming rate, making it hard to use. I was told to go to the BDH service center by Samsung's customer service. Even though the warranty had ended, the authorized service center did not fix the real issue. Instead, they said they had fixed the power problems by replacing my cracked screen, which cost me 1800 TL, even though it wasn't broken. But when I turned on the phone, it shut down and started back up several times in the next 15 minutes. I was so angry that I sent it back to BDH service again right away. The power problem was caused by a bad mainboard, which they didn't find until the second inspection. They then asked for another 1800 TL to fix it. Since I had already paid for it, I asked them to take my old screen as payment for the new mainboard. But they turned it down. The fact that they couldn't find this problem during the first inspection shows that their technicians were either careless or didn't know what they were doing. Both Samsung and BDH didn't give me a phone for a whole month, which was a big problem. I will go to court to protect my rights.