If a contact has several numbers or addresses, a default number or address makes it easier for you to call or send a message to the contact. The default number is also used in voice dialing.
Select Menu > Contacts.
Select a contact and Options > Defaults.
Select a default to which you want to add a number or an address.
Select a number or an address you want to set as a default.
To exit the Defaults view and save the changes, tap outside the view.