Q: touch not responding

Try these standard troubleshooting steps.

Reset: hold down the Home and Power buttons until you see the Apple logo (10-20 seconds).

If this doesn't help, you might need to Restore your iPhone: https://support.apple.com/en-us/HT204184

If your backup is to iTunes, make sure it's an encrypted backup.

Otherwise, take it to an Apple Store for evaluation or replacement.

Usually these two methods will resolve software issues. The only one left is to restore the iPhone as new, then restore a backup, but I doubt it will help.

Looks to me like a hardware issue.

Take it for evaluation to an Apple Store. You said it's a new phone. If under 14 days, you can give it back and get a new one. If older, but still under warranty, Apple will determine if they'll fix it, or give you an "as new" refurbished unit.

I have this too. I updated this morning and my touch screen started responding erratically, so I suspect there may be a causal relationship between the two. My main game is one where you touch squares in a grid, and it's selecting blocks a fair way from where my finger tip touches. Very frustrating. I rebooted, etc., but will not be restoring given my suspicions about the cause. Doing so would lose me certain important data, so I need a damned good reason to restore.