iPhone’s ringer not working

Hello. Sometimes the ringer of my iPhone XR does not work even when I switch it back to the on and off button on the top left of my phone. I even went to the settings of sounds and haptics and put the volume higher and even reset my settings. Its still the same and this is my second time getting this new phone. I dont think there is a defect because my last iPhone XR had the same problem? Is there something I have to change in the settings?