Connectivity Issues After iOS Update on iPhone 11 (Carrier: O2)

cromero_manzana wrote:

I’m experiencing a serious issue with my iPhone 11 after a recent iOS update (from 17 to 18.5) . The device, which was previously working perfectly, now frequently shows no signal or very poor mobile connectivity. Both data and voice calls are affected — it's as if the phone has no coverage.

I use the carrier O2, and when I insert the same SIM card into an iPhone 13 or an Android device, the signal and connectivity work correctly. This clearly suggests the issue is specific to the iPhone 11 after the update.

I have visited an Apple Store twice with the device, but so far, the issue has not been identified. This problem seriously affects the daily use of the phone.

Thank you.

look here If you see SOS, No Service, or Searching on your iPhone or iPad - Apple Support

if the link doesn't help you'll need to contact 02 support.

Your troubleshooting suggests a problem with your phone, not O2, and before considering hardware problems, you should check for any software that will no longer work with iOS 18, in particular remove all VPN, adblockers or security software

If necessary, back up, reset the phone to factory settings and try it set up without recourse to the backup (aka "Vanilla" setup)

Back up iPhone – Apple Support (UK)

Erase iPhone – Apple Support (UK)

Set up your iPhone or iPad – Apple Support (UK)