I want to update my iPhone but you’re not letting me

If you want to update wirelessly, from the phone, you'll need a Wi-Fi connection … and it's a good idea to have the phone connected to power at the same time.

Alternately, if you have a Mac or PC, you might be able to use the Finder/iTunes to manually update the phone.

Update your iPhone or iPad - Apple Support

You can't update using cellular data or a Hotspot.

Can you post a screenshot of the entire screen including signal strength, etc.

Can you clarify the conditions? Are you connected to WiFi?