iPhone XS Max Sound Issue

I purchased my phone last June 10, 2019 and there is no incidents or falling issue occurred and it is still good as new. Software 12.3.1 was updated right after I purchased. 2 days after I bought my iPhone, I experienced of having no sound even it is not on silent mode. I tried flipping the ringer switch on back and forth, reboot, turned off Do Not Disturb feature, dragged the Ringer and Alerts right and left, disconnected all bluetooth devices, reset all content and settings. Yes, it works after doing all of these but this problem is still reoccur and this is my 3rd time today(June 18, 2019) experiencing this problem in my new iPhone XS Max. Is this a software or a hardware issue? What should I need to do?