Customer Management (New Customer Creation/Edit Existing Customer)
When editing customer details, the username should also be editable.
On the same page, only the phone number should be required, not the email address.
Duplicate contacts should not be created based on the phone number. If a phone number is already registered, the system should display an error message like, "This phone number is already in use."
In the Customers Tab, within the customer list, surnames should be displayed first, followed by first names.