What does SOS mean in upper right corner beside Wi-Fi symbol on iPhone?

from

Status icons and symbols on your iPhone - Apple Support

"On your iPhone with Dual SIM capability, you’re in range of your cellular network and can make and receive calls. If there’s no signal, "No service" or "SOS" appears."

If you see No Service or Searching in the status bar on your iPhone or iPad (Wi-Fi + Cellular), your device isn't connected to a mobile network. If you see SOS or "SOS only" in the status bar, your device can still make emergency calls.

If you see No Service, Searching or SOS on your iPhone or iPad