AT&T is warning iPhone 18 Pro Max customers to update their devices immediately as an ongoing cellular issue could prevent affected phones from making calls, sending texts, using mobile data, or even reaching 911.
The carrier has now begun sending text messages directly to customers acknowledging the problem, days after reports first emerged of iPhone 18 Pro Max devices repeatedly losing AT&T service and dropping into SOS mode.
“Action needed,” AT&T’s message begins, before telling customers that some iPhone 18 Pro Max devices may be unable to complete calls, texts, or data connections, including calls to 911. The carrier is instructing users to install iOS 27.0.1 immediately.
The warning significantly raises the stakes around a problem The Apple Post first reported last week, when complaints were centered on unreliable AT&T connectivity and eSIM activation.
At the time, affected owners described devices moving unpredictably between 5G and SOS mode, with calls, messages, and cellular data becoming unavailable despite other AT&T-connected iPhones continuing to work in the same locations.
AT&T’s customer alert is the clearest acknowledgement yet from the carrier that the problem can affect core communications, including emergency calling.
There is an important complication, however: iOS 27.0.1 may not solve the problem for everyone.
Apple’s release notes for iOS 27.0.1 don’t mention AT&T connectivity or eSIM problems. The update was released with a fix for the separate Face ID issue affecting some iPhone 18 Pro and iPhone 18 Pro Max devices.
Some affected AT&T customers also report continuing to experience cellular problems after installing iOS 27.0.1, meaning the carrier’s recommended update doesn’t appear to be a universal fix.
The underlying cause remains unclear. Reports across Apple’s Support Community, Reddit, and other forums describe customers attempting eSIM reprovisioning, carrier troubleshooting, and in some cases replacement devices with varying results.
The U.S. iPhone 18 Pro Max is unusual within Apple’s latest lineup because it continues to use a Qualcomm cellular modem. The smaller iPhone 18 Pro and iPhone Duo use Apple’s C2 modem, as does the iPhone 18 Pro Max sold outside the United States.
There is currently no evidence establishing the Qualcomm modem as the cause of the AT&T issue, however.
For customers who own an iPhone 18 Pro Max on AT&T, the carrier’s advice is to open Settings, select General, choose Software Update, and install iOS 27.0.1 if it isn’t already installed.
Customers who remain unable to reliably make calls, send messages, or use cellular data after updating should contact AT&T or Apple. Given AT&T’s warning about potential 911 availability, affected users shouldn’t assume a phone showing intermittent service will necessarily be able to complete an emergency call.
Apple has not publicly detailed a separate fix specifically for the AT&T cellular issue, and it remains unclear whether another software update or a carrier-side change will ultimately be required.