Fraudulent Uses With My Credit Card

When I tried to purchase a kindle book on Amazon yesterday, my credit card was rejected, so I used another credit card. While I was on the train returning home, I received an e-mail. It was from Rakuten Credit Service, sayng that they detected some fraudulent uses with my credit card. I called Rakuten customer center. Then I was told that someone tried to use my card on Amazon several times yesterday. Eventually, my card was deactivated.