Depending upon what country that you are in then do they show in Purchased tab in the iTunes store app on your phone for downloading ? Music can't be re-downloaded in all countries so you may not have an option for music in the Purchased tab.
If you aren't in a country where you can re-download music then try the 'report a problem' page to contact iTunes Support : 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