Zone of text

Hello,
In the latest version of Illustrator, I'm stuck on a ridiculous problem!
I have some text. I want to adjust the width of the text box without changing the font.
I can't figure out how to do it anymore.
Every time, it makes the font bigger if I make the text box bigger, and vice versa.
The "Adjust Captive Text" preference is unchecked.
I've read the tutorials but still can't do it, and I'm stuck.
How can I change the "text box" without changing the font?
Thank you very much.