You can refund payments within the Stripe dashboard. Search for the payment by its Stripe charge ID, customer ID, or email address. Once you've found your payment, click the Refund Payment button at the top right of the payment view. You can also process refunds directly from the list of payments.
Stripe automatically refunds all of their fees from payments. Stripe doesn't let us know that a refund has been processed, so let Revv know at firstname.lastname@example.org to ask us to refund our fee as well.