Q: The text box is hidden by a grey thing that has 0:00. what is it and how do delete it?

That did the trick.  Per Lawrence we just need to turn off the "raise to listen" option in Settings->Messages.  But, if you don't use iMessage then you'll need to turn iMessage on in order to reveal the "raise to listen" (and other) settings.  Turn off "raise to listen", then turn off iMessage again if you like.  No more grey box.  Hoorah!

Turn on iMessage first. Can disable it after shutting down the Raise to Listen feature.

apple needs to figure out an easier way to resolve this. I spent a week sendig nonsense text messages as I tried figuring out how to get rid of the **** box.  And there's no troublesholting info on apples site regarding the new OS.  I was so irritated with With this I almost threw my iPhone off the balcony 

LOL!  Were you able to get it figured out?

Well done - that worked for us as well on our i5s

Thanks. I turned imessage off and then back on. then when I tried to send a text, the microphone icon finally appeared on the right of the message text box (different from the icon which I select to voice a message) When I pressed the "new" microphone icon, i finally was able to "turn it off". I just saw a red box and then it disappeared.