Hey Hoangluong91.
Welcome to the Community!
In order to cancel a subscription through PayPal, this needs to be done through the 'Settings' page on your account. If you have only cancelled the subscription through the merchant, it's possible that the subscription was never cancelled on the PayPal website. This could explain why you may have been charged again recently.
You can find more information about how to cancel a subscription on your account here .https://www.paypal.com/smarthelp/article/how-do-i-cancel-a-subscription-faq577?app=searchAutoComplet...
I hope this helps.
David.
