Why does my iphone xs freeze and then shuts down

I’ve had my phone for about a month now. The first time my phone froze and shut off I thought it was because the battery was low because it turned back onafyee 5 mins of being plugged in. The second time it happened it was on 99% charge and I was trying to take a photo. The screen froze and then completely turned off and wouldn’t turn back on no matter what I did. I decided to plug it back in and then 20mins later it turned back on. Does anyone know what I should do to fix this issue or had any issues like this the same? Can I even take it back to the shop I bought it from after having it for a month? Laptops and stuff have a year warranty and you can take it back to the store but I don’t think phones do do they?? I’ve paid a lot of money for this phone and I’m scared that I’ve bought a phone that stuffs up and is broken and that I’ll have to pay even more to get it to work properly