Hello TerryW46,
Thanks for using the Apple Support Communities.
I understand that the text size on your iPhone has increased to the maximum setting and you can't reduce it. This is also preventing you from unlocking and turning off the iPhone.
Have you tried to force restart your iPhone by holding both the Side and Volume Down buttons for at least 10 seconds, until you see the Apple logo? If not, please try that. Once your iPhone restarts, notice if the text size has decreased. If it hasn't try a reinstall of iOS.
First, use this article to make sure that you have a backup of your iPhone: How to back up your iPhone, iPad, and iPod touch. Then, use this article to reinstall iOS: If you can‘t update or restore your iPhone, iPad, or iPod touch. Note: This article is intended to be for a different issue but following steps 1-5 will help you reinstall iOS without erasing data.
Let me know how it goes.
Regards.