October 4, 2026 — Apple has confirmed that a small number of iPhone 18 Pro Max users on AT&T's network are experiencing a complete loss of cellular service. The affected devices display SOS mode, cannot make calls, send texts, or use mobile data — and for those already impacted, a software update will not fix the problem. Apple says it will replace the phones for free.

The issue was first reported by users on Reddit and Apple's Support Community shortly after the iPhone 18 Pro Max went on sale in mid-September. AT&T has since sent text messages to affected customers urging an immediate software update. Apple issued a formal statement on October 2.

What Actually Happened

Since the iPhone 18 Pro Max launched on September 18, 2026, users on AT&T's network have reported a specific and severe symptom: the phone suddenly loses all cellular connectivity and enters SOS mode.

The device can still connect to Wi-Fi, but without cellular service it cannot make phone calls, send or receive SMS messages, or use mobile data. In some cases, the loss of service also affects the ability to make emergency 911 calls — which is why AT&T sent urgent text messages to customers.

Thousands of complaints have appeared across Apple's Support Community and Reddit. Some users report that rebooting the device does not restore service.

Who Is Affected (and Who Is Not)

The scope of the problem is narrow but severe for those in it.

CNET confirmed that T-Mobile and Verizon have not seen similar reports, and a CNET colleague using an iPhone 18 Pro Max on Google Fi (which runs on T-Mobile's network) did not experience the issue.

The Modem Difference: Qualcomm vs. Apple C2

One hardware detail stands out. The U.S. version of the iPhone 18 Pro Max is the only model in the entire iPhone 18 lineup that uses Qualcomm's Snapdragon X80 modem.

Every other variant — the iPhone 18 Pro, the iPhone Duo, and iPhone 18 Pro Max models sold outside the U.S. — uses Apple's in-house C2 modem.

The iPhone 18 Pro Max logic board. The Qualcomm Snapdragon X80 5G modem (upper right) is used only in the U.S. model. All other iPhone 18 variants — including China models — use Apple's C2 modem. Image: Tech Insights via iClarified.

What Apple and AT&T Say to Do

Apple's guidance splits into two scenarios: prevention and replacement.

If Your iPhone 18 Pro Max Still Has Service

Apple strongly recommends installing iOS 27.0.1 immediately. Released on September 28, the update is now required during setup of new iPhone 18 Pro Max devices, according to MacRumors.

AT&T has also pushed a carrier settings update that moves the carrier settings version from 72.0.2 to 72.1. It will download automatically for AT&T users over the next 14 days. You can manually trigger it by connecting to Wi-Fi, then going to Settings > General > About and following any update prompt that appears.

Apple's official statement to MacRumors:

If Your iPhone 18 Pro Max Has Already Lost Service

This is the critical part: software updates will not restore service to an already-affected device. Apple says the phone must be replaced entirely.

Affected users should contact Apple Support or AT&T, or visit an Apple Store or AT&T location. Apple has confirmed that replacements will be provided free of charge.

Why China Models Are Unaffected

For readers in China, the key takeaway is simple: this issue does not affect China models.

The reason is hardware. The China version of the iPhone 18 Pro Max uses Apple's C2 modem, not Qualcomm's. Multiple Chinese-language reports have confirmed that the issue is limited to the U.S. Qualcomm-modem variant on AT&T.

No China carrier has reported similar issues, and Apple's support documentation for dual-SIM functionality on China models makes no mention of this problem.

Key Takeaways