iPhone will not update

maybe try going to Settings > General > iPhone Storage.. locate the downloaded iOS version, delete it.

Then restart your phone and check for updates again.

Or use a computer to do the update

Update your iPhone, iPad, or iPod touch - Apple Support

issues?

Updating iOS: common issues and solutions - Apple Community

not enough storage space?

If you need more space for an update on your iPhone, iPad, or iPod touch - Apple Support

video..

Delete the beta profile from the phone, then check again for the proper update.