Make sure your celluar data is turned on!
It’s the little green icon when u pull down on the screen looks like a i with 3 lines around it
Also in your settings go to search and type wifi calling and make sure that’s turned on so you can call people when connected to wifi
Finally make sure to full hard restart your phone for as it is a possibility it could have bugged out.
hold power button and sound down still prompts you with a swipe to shut down.