Apple has confirmed the iPhone 18 Pro Max signal bug: some handsets are losing cellular connectivity because of a fault in iOS 27, and in a rare admission the company says affected units cannot be fixed with a software update. They will need to be replaced.
The iPhone 18 Pro Max signal bug first surfaced in mid-September, when owners reported that their brand new phones could not make or receive calls, that text messages arrived extremely slowly, and that handsets randomly dropped service and fell into SOS mode even while showing full signal bars. Complaints piled up on Apple’s support forums and Reddit before the company acknowledged the fault.
What the iPhone 18 Pro Max signal bug actually does
This is not the usual story of a phone briefly losing signal in a dead spot. Once the bug bites, the iPhone 18 Pro Max fails to reconnect to the mobile network at all, even after a restart. Calls, texts and mobile data all stop working. In the most serious cases, the failure can block emergency calls.
On Apple’s support forums, one owner wrote that their new phone could not make or receive calls or FaceTime, while another said the phone showed four bars of 5G yet could not complete a call.
Confirmed cases so far centre on AT&T customers in the United States. The carrier took the unusual step of texting iPhone 18 Pro Max owners directly, warning that some phones may be unable to complete calls, texts or data, including calls to 911, and urging them to install iOS 27.0.1 immediately. Notably, the standard iPhone 18 Pro and the new iPhone Duo do not appear to be affected.
Apple’s fix: iOS 27.0.1 and a carrier settings update
Apple says it released iOS 27.0.1 earlier this week and strongly encourages all iPhone 18 Pro Max users to update now. It is also pushing out a carrier settings update, which should download automatically within the next two weeks. Owners who do not want to wait can trigger it manually by going to Settings, then General, then About. According to Apple, the two updates together are meant to stop the problem from occurring.
There is a catch. The updates only protect handsets that have not yet been hit. If an iPhone 18 Pro Max is already failing to connect, no software patch will bring it back. Apple says those owners must arrange a replacement through Apple Support, their carrier or an Apple Store.
What UK iPhone 18 Pro Max owners should do
There is no evidence yet that UK networks are affected, and all confirmed cases involve AT&T in the US. But the underlying fault sits in iOS 27 itself, so British owners should treat this as a warning rather than someone else’s problem. If you own an iPhone 18 Pro Max in the UK, take these steps now:
- Update to iOS 27.0.1 straight away through Settings, General, Software Update.
- Check for a carrier settings update under Settings, General, About, and install it if one appears.
- Watch for warning signs: persistent SOS mode, calls failing despite signal bars, or texts arriving very late.
- If your phone already shows these symptoms and a restart does not help, back up your data, then contact Apple Support or your network about a replacement.
Why the Pro Max is hit but the smaller Pro is not
One curious detail is that the bug seems limited to the iPhone 18 Pro Max. In the United States, the Pro Max uses a Qualcomm Snapdragon X80 modem, while the smaller iPhone 18 Pro uses Apple’s own C2 modem. That split may explain why the standard Pro has escaped the problem, although Apple has not confirmed the modem as the cause. Either way, the pattern shows how a single component difference can decide which phones suffer.
The episode is an uncomfortable one for Apple. The iPhone 18 Pro Max is the company’s most expensive mainstream handset, and a fault that can only be cured by handing the phone back is about as serious as it gets. For a closer look at what the phone offers when it works properly, read our iPhone 18 Pro review.
For now, the advice is simple. Update your software, keep an eye on your signal, and if your iPhone 18 Pro Max goes silent and stays silent, do not wait for a patch that will never come. Get it replaced. It is a costly reminder that even the most polished flagship can stumble, and that keeping software current remains the cheapest insurance a phone owner has.
