Battery issue on iPhone 13 Pro Max

I have 3 months old iPhone 13 Pro Max.it’s like brand new condition no cracks or damage at all .I had an issue like 3 weeks ago it started turning on and off and the battery started swelling.the screen lifting off from the side.I took it to the Genius Bar.the guy told me,it looks like an issue with battery.today I received email,my device can not be repaired because of the accidental use or misuse.are you serious Apple ?how come I can damage the inside of the phone which never been dropped.you are not behind your products to fix it or replace the defective phone.Shame on you Apple !