You can't do this yourself, no. I don't know whether our tech team could go in and tell you this - I'll ask and let you know. Can you please send an email to
gmat@manhattanprep.com. In the email, include the text of your post below as well as the name and email address on your account (so that we can look up your test). Ask them to forward the email to me (tell them that I told you this on the forums).
For others who might be wondering something similar - I'll check to see whether it's possible in this case, but note that the ONLY case in which this MIGHT be possible is the exact case described here: it happens on the very last question and the only issue is switching this one question from wrong to right.
Anyone who's wondering whether they can change question 34 from wrong to right and see what would happen from there - we can't do that, because the next question that you would have gotten would have been something else. The entire rest of the test would have changed!