If you haven't already done so then you will need to do as the message says and contact iTunes Support (these are user-to-user forums) :
- go to http://www.apple.com/support/itunes/ww
- click on your country's flag
- click on the Contact Support at the bottom of the left-hand column
- click on Contact iTunes Store Support on the right-hand side of the page
- then Purchases, Billing & Redemption