On the left side of the main menu, click on ORDER OVERVIEW.
Search for the order whose customer data you want to modify.
Open the order by clicking on the order ID.
In the right menu click CHANGE DATE.
Choose the desired date and time slot and click SAVE.
Tip: When you have changed the date and time of the order you can generate the tickets again and then send the confirmation email again. This way the customer receives the tickets again with the new day and time slot. The QR code remains the same.