A response from the iTunes Store customer service group may take 72 hours or more. Response times have increased since they were saddled with handing the Mac App Store as well. Have your received a least the automated acknowledgement of your email, though? If not, you should check any antispam blocker on your email application and/or email account to make sure emails from Apple aren't being trapped out.
Did you ever hear back from them? How did they resolve the issue? I just want to update an expired credit card, but am locked out of the app store etc... Same message. "Please contact itunes support" but no method of contact is provided. Infuriating! My e-mail has been inneffective to date.