If you head to CONTACTS > +ADD CONTACTS you will see an option to Auto-update your existing contacts? Checking this box allows you to overwrite the contact information for a particular mobile number already within your account.
This may be useful if you wish to update a name or perhaps a custom field with new data.
Warning: This will update all fields for an existing mobile number with your new data – this includes removing information already associated with a contact in your account.
