You will place your phone orders in the administration of the reenio reservation system. Creating such a reservation is easy (it can be compared to creating a calendar event).
In addition, if you implement a reservation in connection with a customer's e-mail, you can have an overview of the customer's entire history. If a customer registers with the same e-mail, all of their reservations (regardless of whether they were made by them or you as a part of the administration when ordering by phone) will be accessible retroactively in the system.