How did you redownload it ? If you are in a country where music can be redownload then the page that you posted from tells you how to redownload items - did you use those instructions ? If you did then you shouldn't have been charged.
You can contact iTunes Support via this page (these are user-to-user forums) : http://reportaproblem.apple.com .
If the 'report a problem' link doesn't work then you can try contacting iTunes support via this page : http://www.apple.com/support/itunes/contact/- click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption