How do you fix the cellular data problem?

You will not be able to fix this. The phone will have to be replaced. There is a warranty recall for this problem by Apple. If you're interested, the problem stems from a design flaw in the iPhone board layout where the exact same flexion-damage that caused the iphone 6 plus touch disease epidemic pulls at the baseband power management chip in the iPhone 7. The result is that over time these phones develop an internal short circuit within the qualcomm baseband CPU---the "brain" of the cellular service system in the phone. Since the Qualcomm CPU is unique to each phone, it can't be replaced by your local iPhone logic board repair shop. Apple does not do logic board repairs at all, so their only option is to replace the entire phone. The good news is that unlike the iPhone 6 plus touch disease, this time Apple was very quick to acknowledge this rampant issue and started a recall months ago for this problem.

Doing any further carrier updates, software updates, changing SIMs etc is a waste of time. The exclamation point in the triangle is always associated with the baseband CPU fault which is a hardware problem on the logic board.

Check for a Carrier Settings update

To manually check for and install a carrier settings update:

1. Make sure that your device is connected to a Wi-Fi or cellular network.
2. Tap Settings > General > About. If an update is available, you'll see an option to update your carrier settings.
3. To see the version of carrier settings on your device, tap Settings > General > About and look next to Carrier.

If you insert a new SIM card into your iPhone or iPad, you need to download the carrier settings for your new carrier.

Take out the SIM card and put it back in

If the SIM card is damaged, or doesn't fit in the SIM tray, contact your carrier. Learn more about removing your SIM card.

Reset your Network Settings.

Go to Settings > General > Reset > Reset Network Settings. This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings that you've used before.

If you see No Service or Searching on your iPhone or iPad

I’ve been dealing with this issue since the end of September. Initially, I would lose cell service for a few minutes here and there, but now I’m lucky if it works at all. I had precisely zero issues with my 7 before updating to iOS 12. My phone is now junk thanks to the iOS update and every “solution” offered by Apple is useless. Needless to say, I.am.******.

I’m now awaiting the arrival of my new XR. Under normal circumstances, I would be excited about getting a phone upgrade, but I certainly don’t appreciate being forced to do it.

I’ve tried literally everything, and I have had no luck