If your iPhone won't turn off the usual way, you can force restart it with a button combination specific to your iPhone model.

If you want to fix the SOS displaying on your phone, here's what to do. But the issue may lie with your carrier.

Turning your phone's connection off and then back on is the quickest and easiest way to try and fix your signal woes. If you're moving around from one location to another, toggling Airplane mode ...

If you're not rushing to update your iPhone to iOS 26 anytime soon, these are important iOS 18 settings you can change now.