Carrier Update iPhone 5s

I was on my phone earlier today, and it suddenly said "No SIM Card Installed" I thought that this was strange. I went online and it said your carrier settings may need to be updated. I remembered that little popup that I've been exiting out of that said I need to update my carrier settings. But now when I go to Setting>General>About, there's no prompt that comes up. Please Help! (My phone did have water damage a few weeks ago, but it's recovered now. I don't know if this has anything to do with it.)

Try going into Settings, scroll down to Phone. Click on that and the last thing at the bottom of that menu should be your carrier service. Click on that and see if there's an update there.