IOs12.0.1 froze my iPhone 6d

I assume iOS 12.0.1 was a typo, and you meant iOS 12.3.1. Anyway, the tips in the following should help resolve the issue.

If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support

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

If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support

ninaeisenman wrote:

I tried to update to iOS 12.0.1

This is not possible. iOS 12.0.1 has been obsolete for many (>6) months.

Use (a current version of) iTunes if you cannot update wirelessly.

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