Unauthorized payment
I had an unauthorized payment of $15 taken out of my account for iTunes but I didn’t make any purchases in the last few months.
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If you've looked at the purchase histories of all iTunes accounts you have linked to the card and not found it (and checked iCloud storage) : See your purchase history in the App Store or iTunes Store - Apple Support
and if it's not : About payment card authorization holds from the App Store or iTunes Store - Apple Support
contact the card issuer