First, thanks for the donation. That makes you special to us. :) But, we're just volunteers and the folks in charge don't let us touch the money. This URL is the place to go: https://www.thunderbird.net/en-US/donate/help/

Additional information: https://www.thunderbird.net/en-US/donate/#faq

Quotaion:

Can I request a refund? Your donation may be eligible for a refund. You must contact us within 15 days of payment date. If you believe this payment was made without your authorization, please contact us immediately. Donations made via ACH or SEPA direct debit are ineligible for refunds. Due to the nature of these transactions our policy prioritizes minimizing refund fraud. We appreciate your understanding. If you need assistance, please contact us.

If you want to request a refund, you need to do it quickly.