Is it possible to refund a customer’s new card after their billing info is updated?

When a refund occurs against a transaction, we will always attempt to push that refund through back to the original card that was used to pay for the transaction. If the customer would like to have the refund added to their new card, then you as the merchant will need to reach out to the payment gateway used to process the transaction. They should be able to work with you in order to reroute the refund and ensure that the customer receives it where necessary.