Why can't I see the prior texts?

I just spent hundreds of dollars on a new iPhone 15+ and so far the only benefit is the speaker is louder and more clear. The pictures might be better and I now have a functional battery. However, I probably should've just gotten a new battery for my iPhone 7. It worked great and I could see the prior text to which I was responding. Now when I get into a longer text, I cannot see the text to which I am responding.