Apple has confirmed that an issue is causing a small number of iPhone 18 Pro Max devices on the AT&T network to lose cellular service, according to a statement given to 9to5Mac. Affected users cannot make calls, send texts or use mobile data, and instead see "SOS" in the status bar of their phone.
The company says software fixes are already rolling out to stop the problem from spreading, but any iPhone 18 Pro Max that has already lost service will not recover on its own. Those units require a hardware replacement, Apple told 9to5Mac, and owners should contact Apple Support or AT&T, or head to an Apple Store or AT&T location.
iOS 27.0.1 and carrier settings update
Apple released iOS 27.0.1 earlier this week and is issuing a carrier settings update for the iPhone 18 Pro Max, telling the outlet it "strongly encourages" all owners of the model to install the software now. The two updates are designed to work together to prevent the connectivity failure from appearing on more devices.
The carrier settings update installs automatically over the next 14 days, but users who do not want to wait can trigger it manually by opening Settings, choosing General, then tapping About. Apple is clear on one point: these updates are preventive only and will not bring service back to a device that has already gone offline.
Why iPhone 18 Pro Max is affected and iPhone 18 Pro is not
The difference appears to sit in the modem. 9to5Mac reports that the iPhone 18 Pro Max sold in the United States uses a Qualcomm modem, while the iPhone 18 Pro uses Apple's own C2 modem. The iPhone 18 Pro has not been hit by the AT&T connectivity problems.
Not every iPhone 18 Pro Max owner on AT&T is affected, and Apple describes the number of impacted users as small. Still, the failure is severe for those who meet it, since the phone loses access to calls, messages and data on the network rather than dropping only a single function.
