No WiFi on iPhone 8 - constantly

My daughter and I are both have xfinity mobile and same iPhones.  I find o constantly have wifi issues.  When I look at available networks in settings Xfinity sometimes shows up but lastly doesn’t.  I traveled to Arizona - no service anywhere. Even driving down the road or going to local appointments no wifi or xfinity as an available network.  I always have to log in to public wifi.  All of my settings are correct, don’t know why it’s so sporadic. Getting through to a live person - who is fluent in English - is literally impossible.