I did not purchase an item on iTunes but they keep deducting money from my credit card

Have you downloaded any free items ? Some apps have in-app purchases and/or auto-renewing subscriptions on the. You can view the purchase history on your account via your computer's iTunes : 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. On your iPad you can view the last 90 days purchases, and optionally contact iTunes Support if you have a problem with a purchase, via http://reportaproblem.apple.com

There are instructions on this page for viewing if you have any (and managing and stopping) auto-renewing subscriptions : http://support.apple.com/kb/HT4098

Or have you added or changed your credit card details on your iTunes account ? If you have then each time that you do so a small temporary store holding charge may be applied to check that the card details are correct and valid and that it's registered to exactly the same name and address as on your iTunes account - it should disappear off your account within a few days or so.

Store holding charge : http://support.apple.com/kb/HT3702