Apple has confirmed a hardware defect affecting a small number of iPhone 18 Pro Max devices on AT&T, less than three weeks after the handset launched on September 18. Apple told 9to5Mac it has "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." Devices that have already lost service cannot be recovered through software and will require a full hardware replacement. This is the first significant post-launch issue for the iPhone 18 lineup.
What Is Happening and Why
Reports from affected customers describe phones that cannot send or receive texts or use mobile data, leaving them usable mainly on Wi-Fi and, in some cases, stuck in SOS mode. The problem is isolated to AT&T. Apple has confirmed it has not seen the same failure on T-Mobile or Verizon, and the regular iPhone 18 Pro is not affected on any carrier.
The reason comes down to a modem difference. The iPhone 18 Pro uses Apple's C2 modem, but the US iPhone 18 Pro Max has Qualcomm's Snapdragon X80 modem. iFixit found a new millimeter-wave antenna in the phone, and TechInsights notes that the X80 modem was also used in the iPhone 17 Pro and 17 Pro Max. The failure appears to be specific to how that modem interacts with AT&T's network configuration in a subset of devices, and once it triggers the transceiver does not recover.
If Your Device Has Already Lost Service
Customers whose phones have already dropped service need a hardware replacement. Once a replacement is issued, the line has to be activated on the new handset. How you get the replacement depends on where you bought the phone.
If you purchased through Apple directly, book a Genius Bar appointment for on-site diagnostic verification and same-unit replacement. If you bought through AT&T, process a warranty exchange through AT&T customer support or at a local corporate retail store. If you bought through a third-party retailer like Best Buy, route the exchange through an Apple Authorized Service Provider.
If Your Device Is Still Working, Update Now
Apple released iOS 27.0.1 earlier this week and strongly encourages all iPhone 18 Pro Max users to update now, and is also issuing a carrier settings update. The carrier settings update for the iPhone 18 Pro Max will download automatically over the next 14 days.
Do not wait for the carrier update to arrive on its own. You can force it manually by going to Settings, General, About, and accepting the carrier settings prompt if one appears. The combination of iOS 27.0.1 and the carrier update is designed to prevent the trigger condition from occurring, but it cannot help a device that has already lost service. If your Pro Max is working right now, updating is the single most important thing you can do.
It is also worth noting that businesses that have issued AT&T-connected iPhone 18 Pro Max devices should also plan for temporary communication alternatives while affected employees wait for replacements. If you are in IT and managing a fleet of iPhone 18 Pro Max devices on AT&T, push the iOS 27.0.1 update through your MDM solution today.