Adding the phone is somehow complex, because it is part of the
Address entity, not the
Customer entity (it would be easier to add any of the Customer fields, like
Date of Birth or
So you can add additional fields to the "Create New Customer Account" form by overriding the
But you would need to figure out how to save it correctly, so it can be displayed as the screenshot you attached. I guess it is not possible to save it if you don't create the whole address for the customer (along with address, city, etc).