Hello cml20,
Let's use the steps below to make sure your iPhone is all up to date:
1. Back up your device using iCloud or your computer.
2. Plug your device into power and connect to the internet with Wi-Fi.
3. Go to Settings > General, then tap Software Update.
4. If you see more than one software update option available, choose the one that you want to install.
5. Tap Install Now. If you see Download and Install instead, tap it to download the update, enter your passcode, then tap Install Now. If you don't know your passcode, learn what to do.
You can also find those steps in this resource: Update your iPhone or iPad
You'll also want to check for any updates to your carrier settings using the steps below: Manually update your carrier settings on your iPhone or iPad
1. Make sure that your device is connected to Wi-Fi or a cellular network.
2. Tap Settings > General > About.
3. Follow the onscreen instructions to install your carrier update.
Lastly, let's use the steps below to make sure your Apple Watch is also up to date: Update your Apple Watch
Get ready to update
Next, check these things:
1. Make sure that your Apple Watch is at least 50 percent charged.
2. Make sure that your iPhone is connected to Wi-Fi.
Keep your iPhone near your Apple Watch throughout the update. It could take from several minutes to an hour for the update to complete, so you might want to update overnight or wait until you have time.
Update your Apple Watch using your iPhone
You can wait until Apple Watch notifies you when a new update is available. Tap Update Tonight in the notification, then go to your iPhone to confirm that you want to update overnight. At the end of the day, leave your Apple Watch and iPhone charging overnight so the update can complete.
Or you can update your Apple Watch with your iPhone manually:
1. On your iPhone, open the Apple Watch app, then tap the My Watch tab.
2. Tap General > Software Update.
3. Download the update. If asked for your iPhone passcode or Apple Watch passcode, enter it.
4. Wait for the progress wheel to appear on your Apple Watch. It could take from several minutes to an hour for the update to complete.
Leave your Apple Watch on its charger while the update completes. Don't restart your iPhone or Apple Watch, and don't quit the Apple Watch app. When the update completes, your Apple Watch restarts on its own.
Updating can help to further isolate a potential software conflict.
Should you still be unable to set up your mobile data plan on your Apple Watch, you'll want to reach out to Apple Support: Contact - Official Apple Support They'll be in the best position to look into this further.
Take care.
