Turns out I'm so habituated to hitting the 'Home' key to end a call from using my other cell phones that I'm now doing this on the iPhone as well! Problem is, it doesn't end the call at all. 😐
Instead, I get a green menu bar across the top telling me how I can resume the call! Not what I want. I wonder how many other people are doing this? Frankly, I don't understand why hitting the 'Home' key DOESN'T end a call since it ends all the other applications. Why not the phone?