Link contacts. If two entries for the same person aren’t linked automatically, you can unify
them manually. Tap one of the contacts, tap Edit, tap Link Contacts, choose the other
contact entry to link to, then tap Link.
When you link contacts with different first or last names, the names on the individual cards
don’t change, but only one name appears on the unified card. To choose which name
appears on the unified card, tap one of the linked cards, tap the contact’s name on that
card, then tap Use This Name For Unified Card.
Note: When you link contacts, those contacts aren’t merged. If you change or add
information in a unified contact, the changes are copied to each source account where that
information already exists.
Contacts settings
Go to Settings > Mail, Contacts, Calendars, where you can:
Change how contacts are sorted
Display contacts by first or last name
Change how long names are shortened in lists
Set a default account for new contacts
Set your My Info card
Set if new contacts and updates are automatically derived from mail you receive