In order to edit a customer's name, last name, email and phone number on his reservation order, you need to go to the order page (see instructions here).
Change name, email, phone number (customer info)
You can edit the fields you see in the "customer info" section. Once you complete the changes, click on "save".
You can also change the customer, ie find an existing customer (so you do not have to enter all his details from the beginning).
Click on "change customer" and enter in the search field any of the customer details you are looking for (name, last name, phone or email).
Select the desired customer from the list that appears, by clicking on the magnifying glass. After the change, press "save".
Do not edit reservation orders made online before contacting the customer.