iOS27 - Cell Service Issues

Revert back? Not sure what you are referring to, it has never been possible to downgrade iOS versions.

Check for a Carrier Update:

Manually update carrier settings on your iPhone or iPad - Apple Support

If still no luck, contact your carrier where they can evaluate your cellular connection and signal.

Hi, cellular carriers typically release new firmware with each upgrade and also with most iOS updates. Their firmware is bundled with the iOS updates and upgrades. Carrier firmware updates are meant to improve services, but can also contain bugs and issues with the services they provide. It’s possible this is an Apple issue, but certainly more probable a carrier issue. Not to diminish your experience, but so far you’re the only person reporting this issue.

Specifically, what model iPhone and who is your carrier? Have you talked to the carrier’s support team and if so, what did they say?

Kfos75 wrote:

Since upgrading to the new iPhone 18 pro max with the latest iOS 27 update my AT&T service has 1 bar , more often enough I get sos in intervals of 5 minutes for the past few days lasting hours. Anyone else know or experience this issue

AT&T is currently experiencing an issue with their eSIM's on specifically the iPhone 18. It affects no other cell provider and I suspect they are working on it nonstop as they don't want their customers to switch to T-Mobile or Verizon. It does not affect all users accounts with an iPhone 18, but I have certainly seen quite a few posts and even some that exchanged their iPhone 18 and the results were the same. The same phone on another network provider had no issues.

That suggestion doesn’t work. I now seem to have some cell service but it’s weak. Maybe it’s just random and not related to this iOS update. But it is the only thing I did today.

Yes, downgrade to the previous iOS. This has always been possible by doing it on iTunes and downloading the previous version and by putting your phone into recovery mode. Surprised a level 10 with 95k points doesn’t know this.

KripTed wrote:

That suggestion doesn’t work. I now seem to have some cell service but it’s weak. Maybe it’s just random and not related to this iOS update. But it is the only thing I did today.

Yes, downgrade to the previous iOS. This has always been possible by doing it on iTunes and downloading the previous version and by putting your phone into recovery mode. Surprised a level 10 with 95k points doesn’t know this.

You will find that any previous version will soon no longer be signed by Apple on your device and then it will not be possible to install using iTunes. This happens very shortly after new versions are released. For example iOS 26 users lost the ability to go back to iOS 18 long ago. Currently on iOS 27, you would not be able to go back to iOS 26.6.1 as that version is no longer signed and based on past signing of previous versions, soon iOS 26.6.2 will no longer be signed either and you will be required to have iOS 27 on your device.

You also would want an archived backup and not an iCloud backup to restore to when you were on that version. Your device will be wiped and I have seen all too often where the backup on a newer iOS version gets corrupted if attempting to use it. Very rarely are they backwards compatible.

I should have said "it has never been supported" instead of "possible", because you are correct for a short time that will be possible, although not always without problems, and pretty soon you will not be able to do it at all.

Since upgrading to the new iPhone 18 pro max with the latest iOS 27 update my AT&T service has 1 bar , more often enough I get sos in intervals of 5 minutes for the past few days lasting hours. Anyone else know or experience this issue