I like
Joanna a lot, much more than
Joanne. I think it's refreshing in a sea of
Laurens or Allisons or Megans or Jessicas (I assume they're in your age group). Several years ago, I met a little girl named
Joanna and the name really suited her. Perhaps the reason you get called
Joanne or Joannie is because they're more common than
Joanna. This little girl I met several years ago was the only one I've ever known.