A small number of iPhone 18 Pro Max users on AT&T in the US are facing a network issue that can cut off cellular service. The failure replaces the usual signal bars with an “SOS” symbol, leaving affected devices unable to connect through the mobile network.
Apple confirmed the issue on October 2, 2026, at 10:10 pm EST. The company says the problem can stop calls, text messages, and data over both 4G and 5G, turning a working phone into a device without normal cellular access.
A Network Failure That Shows SOS
The warning sign is clear: the iPhone 18 Pro Max displays “SOS” in the status bar instead of signal bars. When that happens, affected users lose the core services they expect from a phone, including calls, text messages, and mobile data over 4G or 5G.
Apple described the issue in direct terms: “We have identified an issue affecting a small number of iPhone 18 Pro Max users on the AT&T network that may cause a device to lose service and be unable to make calls.” The company has limited the confirmed scope to some iPhone 18 Pro Max devices using AT&T in the US.
That means the issue does not affect every iPhone 18 Pro Max user on AT&T. Apple says only a small number of users are affected, but the result for those users is severe: cellular service stops, and the phone cannot handle calls, texts, or 4G and 5G data.
Apple Pushes Software and Carrier Updates
Apple recommends two updates to help prevent the issue: iOS 27.0.1 and a carrier settings update. Apple has issued the carrier settings update and encourages users to install iOS 27.0.1, creating a clear prevention step for iPhone 18 Pro Max users on AT&T.
The updates matter before a device loses service. Installing iOS 27.0.1 and the carrier settings update is Apple’s recommended way to prevent the network issue, so users with working cellular connections have a direct action to take.
- Install iOS 27.0.1.
- Install Apple’s carrier settings update.
- Take both steps before the iPhone loses cellular service.
The situation changes once the phone has already lost its connection. Apple says a software update or restore will not fix an iPhone that has already lost cellular service, so affected users must get the device replaced.
The Modem Difference Inside Apple’s US Lineup
The iPhone 18 Pro Max stands apart from Apple’s other US models because it is the only US model that uses a Qualcomm modem instead of Apple’s own modem. That hardware difference sits at the center of this network issue, which affects the iPhone 18 Pro Max on AT&T.
The modem connects the device to cellular networks, making the failure especially disruptive when it appears. Once the status bar changes to “SOS,” the phone loses access to calls, text messages, and data over 4G or 5G, and Apple says replacement is required if service has already disappeared.
For users who still have service, the path is straightforward: install iOS 27.0.1 and the carrier settings update. For users whose iPhone 18 Pro Max already shows the SOS symbol and has lost cellular service, updating or restoring the phone will not solve the problem.
Apple’s confirmation gives affected AT&T customers a clear line between prevention and repair. Updates can help prevent the issue, but a device that has already lost service must be replaced, making the status bar an important signal for what happens next.
The confirmed problem remains limited to a small number of iPhone 18 Pro Max users on AT&T in the US. Still, the lesson is immediate: on this model, an SOS symbol can mean more than a weak connection. It can signal a cellular failure that software cannot repair after the service is gone.
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