By default, customer profiles require a valid phone number on file. If your company does not require phone numbers for passengers, you remove this restriction. By going into your "Company Details", you can disable the option for "Customer phone numbers are required."
This will cause the following changes:
The "New Booking" form will not require phone numbers for passenger profiles
Creating new customers from the "Customers" section will no longer require a phone number
Admins can remove phone numbers from users who have previously added a phone number
Important note: Users who create email/password accounts will still be required to enter a phone number.