In a statement shared with MacRumors on Friday, Apple said that iPhone 18 Pro Max users who have experienced an issue where ATT cellular service does not work will need to have the device replaced, as the issue apparently cannot be fixed with a software update once it has occurred. This requirement is a big deal, as it hints at hardware failure, but we lack details since Apple and ATT have yet to disclose the underlying cause of the issue. A spokesperson for ATT directed us to Apple, which has yet to respond to our latest request for comment. It is possible that Apple is still investigating the issue, but so far our follow-up questions have been met with radio silence (pun intended). In the meantime, all we know is that Apple said iOS 27.0.1 and an ATT carrier settings update released last week "are meant to help prevent this issue from occurring," so iPhone 18 Pro Max users who have not experienced this issue should ensure that both of these updates are installed immediately to avoid potential future impacts. To install iOS 27.0.1, open the Settings app on your iPhone and tap General → Software Update. The carrier settings update for the iPhone 18 Pro Max will automatically download for ATT users within the next 14 days, according to Apple. To manually trigger the update, users can open the Settings app and tap General → About. Apple said it has only observed this issue with iPhone 18 Pro Max users on the ATT network. No other iPhone models or carriers are known to be impacted. Notably, U.S. models of the iPhone 18 Pro Max rely on Qualcomm's Snapdragon X80 modem for cellular connectivity, while variants of the device sold in all other countries are equipped with Apple's custom C2 modem. It is unclear if this modem difference is a factor in this ATT issue, or if the overlap is merely a coincidence. We have reached out to Qualcomm and will share the company's response, if any. Apple said a "small number" of iPhone 18 Pro Max users experienced this ATT issue, which prevents phone calls, text messages, and cellular data from working. A "small number" is Apple's standard wording for these types of issues. Thousands of users have complained about the issue across the Apple Support Community and other platforms.Related Roundup: iPhone 18 ProBuyer's Guide: iPhone 18 Pro (Buy Now)Related Forum: iPhoneThis article, "Apple and ATT Have Yet to Explain Cause of iPhone 18 Pro Max Issue" first appeared on MacRumors.comDiscuss this article in our forums ...read more read less