Phone issue

My iPhone can’t make or receive calls. It said it needed an update in order to get my cellular data back. Updated it, worked for a little while. Then back to no service so plugged it back into the computer and made it update again, worked for a while, now back to no service and keeps turning on and off. With everything going on in the world I can’t go to Best Buy to buy a new phone. Wondering if there’s anything I can do