You can change your booking details at any time. However, the sellers are not under any obligation to accept your changes. To do this, please click on the menu item "Buy" - "My bookings" and go to the "Details" of the booking concerned. There you will see a button marked "Change booking". Click on it and make the desired changes. The seller will be informed of your request immediately and will be asked to process it. You will be informed by e-mail as soon as he has implemented or rejected the change.