Why is my phone always in a Searching mode?

Why can’t I connect to to my telephone provider (AT&T) . The phone goes into a Searching mode; now I don’t have phone service. And because it’s always searching it’s draining the battery real fast. So I'‘m having to power the phone off to save on battery life.

What do you think is happening? I’ve gone through all the settings— but no change.

I do have WiFi.

Thanks for your help,

Henry Sanchez