it won’t let my cellular data turn on.

First, go to Settings/Screen Time/Content & Privacy Restrictions/Cellular Data Changes and see if it says Allow, and change it if it doesn’t.

Next, read and follow the guidance in the Related Article at the top of this page→If you see a Cellular, Ultra Wideband, or Apple Pay Issue message after an iOS update or restart

If that doesn’t resolve the problem go to Settings/General/About and look at Modem Firmware. Is the entry blank? If it is you need to reinstall it by restoring the phone to factory settings, then restoring a backup. Back up the phone first, of course:

1. How to back up your iPhone, iPad, and iPod touch - Apple Support
2. Restore your iPhone, iPad, or iPod to factory settings - Apple Support - follow the instructions to restore using your computer, do not using Settings/General/Reset (which is not included in those instructions)
3. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

If the modem firmware DOES have a value you may have a hardware problem. The first step is what I just posted, but after that you need to contact Apple support using the Get Support link at the top of this page.

Hello~ Any help here by clicking on below?

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

Post back if needed and take care.

~Katana-San~