Reports: There is no Apple support page for this yet. The details below come from a statement Apple gave to 9to5Mac and MacRumors on October 2, 2026, and from AT&T's statement to MacRumors.
Apple said it 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. Apple said it released iOS 27.0.1 earlier this week and strongly encourages all iPhone 18 Pro Max users to update now. It is also issuing a carrier settings update, and says the two updates together are meant to help prevent the issue.
According to the reports, the carrier settings update downloads automatically to the iPhone 18 Pro Max over the next 14 days. Users can trigger it by opening Settings, then General, then About.
The updates are meant to prevent the problem. They will not restore service on a phone that has already lost it. Apple told the outlets that those devices need a hardware replacement, and affected customers should contact Apple Support or AT&T, or visit an Apple Store or AT&T location. MacRumors reports Apple said it has only observed the issue on iPhone 18 Pro Max phones on AT&T.
AT&T told MacRumors that Apple released a software update for an issue that may affect calls, data, texts and 911 calls on a small number of iPhone 18 Pro Max phones, that customers should update now, and that it is working with Apple. Apple has not disclosed the cause.