Recently, a large amount of money was withdrawn from my card without my consent

Contact your Bank, then contact Apple Support.

If it shows on the purchase history of any iTunes account you've got linked to the card contact iTunes Support : http://www.apple.com/support/itunes/ww (click on your country's flag, the country where you live, and which is therefore the country on the account ; click on Contact Support towards the top right ; click on Get Help under 'Talk To Us’)

If they don't show on your iTunes account(s) contact the card issuer.