Strange contacts behavior in Messages

I am trying to help a friend fix a problem in Messages. Whenever he wants to start a new text message, he types in the persons name and it only shows him emails not phone numbers. They are all people he has texted before and their phone # is listed in the contact entry. He is a PC user that uses an iPhone. How can he get Messages to show the phone number and not the email of the person he is trying to start a new text with?