Cellular data update failed

Follow these steps:

Before proceeding, make sure that you have a backup of your iPhone or iPad. Then follow these steps to reinstall iOS or iPadOS:

1. Connect your device to a computer. Make sure you have the latest version of macOS or iTunes. On a Mac with macOS Catalina 10.15, open Finder. On a Mac with macOS Mojave 10.14.4 or earlier, or on a PC, open iTunes.
2. If you see a "Trust this Computer" alert, unlock your device and tap Trust.
3. Select your device.
4. In Finder, click General. Or in iTunes, click Summary, then follow these steps:

• • On a Mac: Command-click Check for Update.
  • On a Windows computer: Control-click Check for Update.

Your computer will download and reinstall the current version of software on your device. Don't disconnect your device from your computer until the download completes.

If you continue to see either of the alerts above, take your iPhone or iPad to an Apple Authorized Service Provider or make a Genius Bar reservation at an Apple Store. You can also contact Apple Support.

Source: https://support.apple.com/en-us/HT208733

Try restarting your device.

We have been tried all the things