Tablein saves guests by phone number, using their phone number as an ID. For this reason, please DO NOT use the same phone number for different people. If you cannot ask for a guest’s phone, it is better to leave a phone number field empty.
When you add a phone number or name to a search field, all information about the guest appears. For this reason, the wrong people get emails from you, because the system thinks that he booked a table again.
When you use the same number, the system updates the information for all bookings. It uses the last information entered. So when you move the reservation, it is updated and the name might change. For example, if you add reservation under name John and later with same phone number- Julia, all reservations with this phone number will be updated to Julia.
You can turn off the phone number requirement here - https://app.tablein.com/settings/reservations-settings
(for online reservations it is always a must).