My observation is that when "normal" Americans see a oddly spelled name they automatically think it's foreign and start to try to pronounce it as it it were since many foreign names for some reason are not spelled phonetically. I fall victim to this a bit too since I would with foreign people on a daily basis. If I saw Joshem, I would think Joe-shum because it looks Hebrew.
Also, my wife's name is Chanin (pronounced Shannon). She gets Cha-nin and Cha-neen a lot.