Hi @Jingchen Hu — welcome to Figma Forum! A quick note: Support here is isn’t available in the Chinese language, so I hope it’s okay I’m continuing forward in English. I've removed the number from your post to keep your account details private.
I understand you meant to buy a monthly membership but were charged for an annual one. Since I can't review billing from this public thread, I'm connecting you with Customer Support. You mentioned two options that would work — a refund so you can repurchase monthly, or switching to monthly with the difference refunded — and Customer Support can review both.
Your case number is: 2087388, and the team will follow up at the email tied to your Figma account. 🙏🏻