Galaxy s9 incoming text message changes font size from original message

[Soxxie]

When I first get a text message, the font size is great, but when the message is too long for the first page and I need to click to the second page to finish reading the rest of the message, the font size dramatically shrinks to a tiny size. And I cannot find anywhere I can change the setting for this. What is going on. Can someone please help me? Or does anyone else have this problem?

 

[ManiacJoe]

Galaxy s9

Which version of android?
Which carrier?
Which SMS app are you using?