I Have a Problem With My Poco X7 From N11 Because It Shuts Down on Calls

My Poco X7 phone, which I bought through N11, has been giving me trouble for about four months now. At the 29th second of calls with certain numbers, the phone turns off by itself. The issue was fixed for a short time, but it started up again and is still happening. Up until now, I haven't had any other computer issues. My phone is still under protection, and I have the proof of that. I haven't talked to the official service or customer service yet. When I bought the thing, I paid ₺18,000 for it, and I'm using it in Gaziantep. I want this problem to be fixed and, if possible, the money back for the goods.