Amid a massive wireless service outage that affected customers of numerous providers across the country Thursday, many people reported seeing SOS on their iPhones and some were urged to use wifi calling if needed -- but what do those mean?
The questions surfaced as thousands in the Chicago area and across the U.S. lost power and service amid a massive AT&T outage.
Messages and alerts popped up on cell phones across the country as emergency responders warned that many users were unable to reach 911 call centers as a result.
At its peak, more than 70,000 outages were reported.
“Some of our customers are experiencing wireless service interruptions this morning," AT&T said in a statement Thursday morning. "We are working urgently to restore service to them. We encourage the use of Wi-Fi calling until service is restored.”
Just after 10 a.m., the company reported outages were still ongoing but three-quarters of the network had been restored. A cause for the outage has not yet been released.
So what should you know if you are without service now or again in the future?
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Here's an explainer:
What is SOS mode and why is your phone showing it?
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Some AT&T customers reported to NBC Chicago that the message "SOS" appeared in the upper right corner of their phone where service bars typically appear.
According to Apple, that message appears when "your device isn't connected to your cellular network," but it also means you can make emergency calls through other carrier networks.
The feature is only available in the U.S., Australia and Canada.
"When SOS appears in your iPhone status bar, it means a cellular network is available for emergency calls," the company says.
Those who make a call with SOS will automatically go to a local emergency number and their location will be shared with emergency services.
Users can also set up their phonse so that after they make an emergency SOS call, their phone alerts emergency contacts with a text message that includes their current location -- and will update those contacts if that location changes.
"On iPhone 14 or later (all models), you can even use Emergency SOS via satellite to text emergency services when no cellular and Wi-Fi coverage is available," Apple states.
What is wi-fi calling?
For those experiencing a service outage, but who still have wi-fi, they'll still be able to make calls.
Just look for "Wi-Fi" in the status bar to see if it's available to you.
"With Wi-Fi Calling, you can make or receive a phone call if you have a Wi-Fi connection in an area with little or no cellular coverage," Apple states.
And it's not just for Apple users.
According to AT&T, "Wi-Fi Calling lets you talk and text over an active Wi-Fi connection" and most Apple and Android smartphones since 2015 support it. Users will "still need a smartphone with an eligible rate plan for it to work," however.
"You can turn Wi-Fi Calling on or off in your phone’s settings. With Wi-Fi Calling, you can call, text, and use AT&T Visual Voicemail as you do on the cellular network," the company's website states.
How can you turn on wi-fi calling?
Here's what Apple says to do:
Go to Settings > Phone > Wi-Fi Calling. You might need to enter or confirm your address for emergency services.
