If you wish to permanently remove an existing contact, you need to delete the contact.

To delete a contact: 

1.To delete a contact, simply select the contact, and right-click on the selected contact. On the context menu, select the "Delete contact..." option. A confirmation message will be displayed: 

"Delete Mike Davies from your list of contacts? This operation cannot be undone!"  (Mike Davies is the name and surname of the contact, as per this example).

Make absolutely sure that the correct contact is selected. If you click on the Yes button by accident, you need to create and add / enter all the details.

2.Click on the Yes button. The contact will be removed from the list.