You can make changes to a Booking after its been marked as Completed so long as you have not charged the Customer yet.
If you’ve already charged the Customer, simply refund the amount that was charged for the Booking first, then make your changes to the Booking.
If you only need to refund part of the amount that was already charged, you can issue a partial refund in Stripe:
- Log in to Stripe
- Click on the Payments link from the navigation menu
- Click on the payment for that booking
- Click on the Refund Payment button
- Choose to issue a Partial Refund
- Enter the amount that you would like to refund
- Click Refund