Apple says some iPhone 18 Pro Max units that lose AT&T cellular service cannot be repaired through software and must be replaced. The company has not identified the underlying cause, leaving open questions about whether the failure involves the phone’s hardware, the AT&T network, or both.

The issue prevents affected devices from making calls, sending text messages, or using cellular data. Apple said it has seen the problem only on the iPhone 18 Pro Max when connected to AT&T. No other iPhone models or carriers are currently known to be affected.

Apple recommends replacing affected phones

According to Apple, an iPhone 18 Pro Max that has already developed the problem cannot be restored by installing a software update. Owners experiencing the failure will need to contact Apple or an authorized service provider about replacing the device.

AT&T has directed questions about the issue to Apple. Apple has not provided an explanation for the failure or clarified whether its investigation is still ongoing. The company has described the number of impacted customers as “small,” although thousands of users have reported similar problems across Apple’s support community and other online platforms.

Updates are intended to prevent the failure

Apple said iOS 27.0.1 and a recent AT&T carrier settings update are designed to help prevent the problem from occurring. The updates do not repair devices that have already been affected, but installing them may reduce the risk for users whose phones continue to work normally.

To check for iOS 27.0.1, open Settings, select General, and then choose Software Update. The AT&T carrier settings update is expected to download automatically for iPhone 18 Pro Max users within 14 days, according to Apple. Users can also check manually by opening Settings, selecting General, and tapping About.

Modem differences add to the uncertainty

U.S. versions of the iPhone 18 Pro Max use Qualcomm’s Snapdragon X80 modem for cellular connectivity. Models sold in other countries use Apple’s custom C2 modem. Apple has not said whether the modem difference is related to the AT&T problem or is simply coincidental.

That distinction may become important if further reports show that the failure is limited to U.S. hardware. For now, however, there is no confirmed link between the modem design and the AT&T service issue.

What affected owners should do

iPhone 18 Pro Max owners on AT&T who still have service should install both the latest iOS release and the available carrier settings update. Anyone who has lost calls, texts, and cellular data should contact Apple rather than expecting a future software update to restore the device.

Until Apple or AT&T provides more technical information, the scope and cause of the failure remain unclear. The replacement guidance indicates that Apple is treating affected units as a hardware-level problem, but the company has not confirmed which component is responsible.