I do not think there is a way to get a new wand. Only in case that it is severly broken you are allowed to get a new one, but this is unlikely to happen at HOL.
What makes you hate your wand? But in case if you really want a new one, you can just sign up in Wands Workshop Class with Prof. Ulol Kimil.. You'll make a new one on your own..
Thanks!! actually, I am attending Wands Workshop, and i made my new wand, but I don't know should I just send an e-mail to prof. Kimil, or how?? And I hate my wand because he is too short for my expectations, I don't like the core...
I know that sometimes your wand physically disappoints you. But, however, your wand represents your character, doesn't it? You answered the questions honestly, and then you got your wand. It's better than not having any wand right? Be grateful!