When you add a credit card to your account (or re-confirm it when adding a new device), Apple will make a small pre-authorisation (less than £2.00) to confirm the details. It's only an authorisation and should disappear in a week or so and should never appear on a monthly credit card statement.
If this is a charge that has made it to your monthly statement, then it's not the validation pre-authorisation and you need to question it