Phone won't work

I Have the iPhone 11 and yesterday my phone kept randomly shutting down. When I would turn it back on the wifi and bluetooth were greyed out and it said my cellular will not work until I update my phone. I reset the network settings and got the wifi back. When I tried to update my phone it would never work. Just last night my phone turned off again and greyed out the wifi and bluetooth but this time when I reset my network settings it did not go back to normal. So now absolutely nothing works on my phone and it won't let me update. Help!