I have searched around for the problem and all I get is the size of the actual messages that I can easily change with the D-pad. I have also changed the text size through the options in settings.
My problem is basically just how do I change the size of the stuff that I type in the box before sending a text message? Not really sure how to word it very well so I'll just post a picture.
EDIT: Apparently even after I had set the text size to what I want countless times, I tried once more like Unknown Zone said even though I knew I had it set right. I hit okay and its the correct size now.