Apple has informed users of the iPhone 18 Pro Max experiencing AT&T cellular service issues that replacements are necessary, as the problem cannot be resolved with a software update after it has occurred. This suggests a potential hardware failure, but details regarding the root cause remain undisclosed by both Apple and AT&T.
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An AT&T spokesperson referred inquiries back to Apple, which has not responded to follow-up requests for additional information. It remains unclear if Apple is still investigating the matter, as no further comments have been provided.
To help mitigate this issue, Apple mentioned that iOS version 27.0.1 and a recent AT&T carrier settings update are intended to prevent the problem for unaffected users. iPhone 18 Pro Max users are advised to ensure these updates are installed. To update to iOS 27.0.1, users can go to the Settings app, select General, then tap Software Update. The carrier settings update will automatically download for AT&T users within 14 days, but can also be initiated manually in the Settings app under General and then About.
Apple has stated that this AT&T-related issue is observed only among iPhone 18 Pro Max users on the AT&T network, with no reports indicating that other iPhone models or carriers are affected. Notably, the U.S. variants of the iPhone 18 Pro Max utilize Qualcomm's Snapdragon X80 modem for cellular connectivity, while models sold in other countries feature Apple's custom C2 modem. It is not yet determined if this modem discrepancy is related to the issue.
Apple described the affected group as a "small number" of users, though this phrase is typically used by the company for such incidents. However, complaints regarding this cellular issue have been frequent across the Apple Support Community and others.