When you pre-order an album you aren't charged until the album is released - if tracks are released from the album ahead of the actual album's release then you will be charged for those individual tracks (at their full price), with the remainder of the albums's price being paid on the album's release.
Pre-orders : http://support.apple.com/kb/HT5714
If you cancelled the pre-order then the released tracks will remain as purchases on your account, you will not be refunded for those tracks.
Do they show as purchased in the store and do they show on your account's purchase history ? If you log into your account on your computer's iTunes via the Store > View Account menu option, you should then see a Purchase History section with a 'see all' link to the right of it. Click on that and you should then see a list of your purchases.
The HT5714 page that I linked to includes :
Some pre-orders include songs that are available for download immediately. When you pre-order, you will be charged only for these songs and you will receive them immediately.
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