Somebody changed my Payment Method

Hi,

This morning I woke up to a bunch of e-mails saying my Apple ID information has been changed and that I had purchased over 400 euros worth of some kind of Chinese app. My first instinct was that this is a phishing scam, so I ignored the mails & changed my Apple ID password on my own accord, just to be sure. I didn't follow any of the links from the mail.

However, I checked my account information. To my shock, I saw that there was an unknown MasterCard number added to my Payment Method. I don't own a credit card, and have thusfar always paid for music/apps via iTunes giftcards. I don't plan on ever changing that. However, I can't seem to select "none" as my Payment Method anymore since the creditcard got added.

Also, in my Purchase History, the 400 euros worth of Chinese app-purchases are visible. So I'm just a bit confused about what's going on here. Clearly, this seems more like a hack than a phishing scam.

I've sent Apple Support an e-mail, but figured it would be good to ask other people for advise too. Is this going to be a problem for me? They haven't robbed me, I had nothing left in my Store Credit, and the creditcard isn't mine.

What should I do?

Kind regards

Renée