Hi Jaehyun,
We’re very sorry to hear that you’ve had some suspicious transactions on your credit card. All of our payments are handled by PayPal, so all payments actually take place through them. We don’t actually store your credit card information on our servers, but we had a developer look into it just in case, and he assured us that nothing was “leaked” from our site.
You may also want to contact PayPal (402-935-7733) just to be sure nothing has happened on their end. Let us know if we can do anything else to help you!