https://support.apple.com/en-us/HT213426
To connect to a satellite, you need to be outside with a clear view of the sky and horizon. When you use a satellite connection, the experience is different than sending or receiving a message via cellular.
Learn more about connecting to a satellite with your iPhone
Emergency SOS via satellite is free for two years after the activation of an iPhone 14, iPhone 14 Pro, iPhone 15, or iPhone 15 Pro.
If your iPhone or Apple Watch detects a severe car crash or a hard fall and you're unresponsive, an automatic Crash Detection or Fall Detection notification to emergency services may be communicated by your iPhone 14, iPhone 14 Pro, iPhone 15, or iPhone 15 Pro using Emergency SOS via satellite if you're outside of cellular and Wi-Fi coverage.
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https://support.apple.com/en-us/105097