Apple India — not replaced my iphone though it was in their warranty period

Address:

Kolkata, West Bengal, 700033

I bought the iPhoneX last year on the month of December and this year suddenly the phone stopped on its own and being within the warranty period I showed it to an authorized service center in South Kolkata. After checking the phone minutely they asked me to submit it and they mentioned particularly that the phone wasn't opened by any other party. They told me that they have to send it to their office in Bangalore. My phone stopped working due to a hardware issue of apple itself. In this case the sole responsibility of the company is to replace with a new one but now Apple is totally ignoring the matter and instead blaming me that the phone has been opened by some other party. Now without any relevant cause they sent back my phone in dead condition to their service center where we submitted.
After investing so much money for such phones and suffering as a customer is our destiny now?? Though it is under warranty period and used carefully.