How come ive been charged from my debit without purchasing anything from the itune

This is a user-to-user support forum. The following link has instructions on how to see the purchase history so you can see what it was that you were charged for. It also has a link to contact iTunes store support if you need to do that. See your purchase history in the iTunes Store - Apple Support

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 the same name and address as on your iTunes account - your card issuer should remove it from your card within a few days or so.

Store holding charge : About payment card authorization holds in the iTunes Store - Apple Support