I understand that there is an unintentional purchase made on your iTunes Store account. Sometimes even I often unknowingly purchase the items and I know how concerning it is. I will look into this issue and provide you with the necessary information.
Phattarapon, I reviewed your account and found that there is an unpaid order on it. To resolve your issue I request you to clear the Unpaid order on your account. The Unpaid orders will also temporarily prevent you from purchasing.
For your information you can pay for this order with a different credit card or with store credit.
To review what the purchase was for and how to pay for the order, see the steps in this article: