Apple confirms AT&T defect stranding iPhone 18 Pro Max users in SOS mode

Apple has confirmed a cellular defect affecting a small number of iPhone 18 Pro Max users on AT&T's network in the United States, causing devices to lose service and drop into SOS mode. The company released iOS 27.0.1 and a carrier settings update intended to prevent the problem, but phones that have already lost signal cannot be fixed by software and require a free hardware replacement.engadget.com

The confirmation follows a wave of complaints from iPhone 18 Pro Max owners who reported their phones switching to SOS mode, disabling calls, texts and mobile data over 4G and 5G while Wi-Fi continued to work. Apple said the issue affects only a small number of users, and AT&T warned customers the problem could prevent calls to 911, urging them to install iOS 27.0.1 immediately through Settings, General, then Software Update.zdnet.com

What Apple confirmed

Apple's statement, shared with 9to5Mac and ZDNET, reads: "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 said it released iOS 27.0.1 earlier in the week and is issuing a carrier settings update to help prevent the issue from occurring.heise.de

The updates are preventive rather than curative. Apple said iOS 27.0.1 and the carrier settings update together are meant to stop the defect from happening, but they cannot restore service to a phone that has already dropped its signal. Owners in that situation must contact Apple Support or AT&T, visit an Apple Store or AT&T location, and request a free hardware replacement.

The US iPhone 18 Pro Max is the only model sold in the country that uses a Qualcomm modem rather than Apple's own chip. A teardown by iFixit, cited by CNET, shows the US version uses Qualcomm's Snapdragon X80 modem, the same chip found in the iPhone 17 Pro and Pro Max, while other regions use Apple's Baseband C2.

Why the modem matters

The modem alone does not explain the failure, since the Snapdragon X80 worked without issue in the previous generation. Heise reported that the iPhone 18 Pro Max appears to add a new millimeter-wave antenna, though neither Apple nor AT&T has linked that antenna to the service failures. Apple and AT&T have not publicly explained the cause, and the underlying reason remains unconfirmed.

Apple released an AT&T carrier settings update, version 72.1, up from 72.0.2, and began requiring iPhone 18 Pro Max users to install iOS 27.0.1 in order to set up the device. A leaked AT&T email said iOS 27.0.1 is meant to help mitigate future impacts, though most affected users said the update does not resolve their existing issues.

What affected owners should do

AT&T has texted customers warning of an "important Apple Software update" and telling them to update to iOS 27.0.1 immediately. The carrier said some phones may be unable to complete calls, texts or data, including to 911. AT&T also said it is working with Apple, and its statement added: "Our top priority is ensuring customers can stay connected when they need it most."

The carrier settings update will automatically download for AT&T users over the next 14 days, according to Apple, and can be manually triggered by opening Settings, tapping General, then About.

Owners who have not yet lost service should install iOS 27.0.1 and confirm they have the latest carrier settings by opening Settings, General, then About. Those who have already lost signal should contact Apple Support or AT&T and request a free replacement, explaining the model, carrier and whether they installed both updates. It remains unclear whether a follow-up update like iOS 27.0.2 will be needed.