Have you bought a day ticket with a variable price (Day Ticket 2020)? Then rebooking is not possible. You can cancel the ticket up to 2 weeks after purchase and place a new order.
Do you have another ticket such as a family ticket or flex ticket? Then rebooking is possible. Please contact us for this and we are happy to help you! Rebooking is possible until 3 January 2021 at the latest.