Hi, @김하늘. Apologies for replying in English - I don’t speak Korean.
Were you canceling a Professional subscription? You might want to review our help article on managing billing on the Professional plan, especially if you think you will upgrade again in the future. It helps explain what to expect when you add and remove seats.
Having said that, I’ve created a ticket for you with our support team since we can’t directly assist with account and billing issues here in the forum. You should get that via email shortly. Let us know if you have any other questions - happy to help!