unknown charge

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If you have never done business with Apple, the Apple links will be useless for this and you could suffer costly delays in resolving this.

You need to work this through your credit card issuer. Someone has gotten you number and is using it.

We had that happen with an AMEX card, seeing small charges under US$5 in several Eastern US cities we'd never been. My wife let the credit card company know about them and the were removed, but later we found out there had been an attempt to charge close to US$400 in the Detroit area.

AMEX said small charges are tests of the number and then there is a big one. The fact that we took timely action on the small ones stopped the big one.

We cannot do that for you and nether can Apple, so call you card company as soon as possible.