Can’t use my phone

The 'update' the message is referring to is a cellular update, not an iOS update, as I experienced on my old 6S.

Go to Settings > General > About. If there's a cellular update that needs to be installed, a message will come up after several seconds. If not, then Contact Apple Support

If you are seeing 'No Service' on your phone, see > iPhone 7 Repair Program for "No Service" Issues

Also > If you see a Cellular Update Failed or Apple Pay Not Available alert after iOS update or restart

Hello and thanks for posting.

I understand that you are having problems with cellular connectivity. What I recommend doing is trying to see if you have a carrier 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.

[pulled from here]

If that doesn't help, try doing a network reset.

On the affected iPhone, go to Settings. In settings, go to About > Reset Network Settings

Doing this will help with any bad carrier updates you may have gotten, but id try the network reset last, as your iPhone will forget every WiFi network you've very connected to.

Hope this helped!

~ TurtleGlo