If people don't want other people to mess up their names then they shouldn't have hard to spell names in the first place.
Don't worry. A lot of people still don't do the follow-up after an interview so I think you are already way ahead of the game.
Hey, it's not like we all pick our names! Everyone spells mine "Rahkee" instead of "Rakhee". I don't even correct people anymore.
I love it when managers who don't know what I look like come into a room looking for me and mispronounce my last name. Gives me an excuse to ignore them. If you can't be troubled to pronounce it correctly, then I can't be troubled to listen to you.