I went to merge two duplicate contacts on my iPhone this morning and noticed the option to merge -- or link -- them was gone. In previous iOS versions, a Linked Contacts section at the bottom of the Edit screen in the Phone or Contacts app let you link two contacts where you had, say, one with a person's home phone number and another with that person's cell number or e-mail. After hunting through a few Apple forums, I found the solution.
When iOS 6 was released last fall, it featured tighter integration with Facebook. After updating, my iPhone's contact list was littered with all of my Facebook friends. I found a way to remove my Facebook friends from my iPhone's contact list, leaving only the contacts I had entered for a much more manageable list. Turns out, when I disallowed Facebook from accessing my contacts, I lost the ability to link contacts.
So, if you have duplicate contacts you'd like to merge and, like me, had previously severed the tie between Facebook and your iPhone's contacts, you'll first need to restore that connection. Don't worry, as soon as you link your contacts, you can again give Facebook the boot from your contacts and your linked contacts will stay linked.
To get started, go to Settings and scroll down until you see Facebook. On the Facebook settings screen, tap to turn on the slider for Contacts in the Allow These Apps to Use Your Account section.
Now, open your Phone or Contacts app and find the duplicate contacts you'd like to merge -- or link, in iOS' parlance. Tap on one of the duplicates and then tap the Edit button in the upper-right corner.
From the Edit screen, scroll down to the bottom where it says Linked Contacts. Tap the Link Contact button and choose the other duplicate you'd like to merge.
Next, you'll see the second duplicate you've chosen to link. Tap the Link button in the upper-right corner to link the two contacts.
Next, you'll see the one linked contact with the two sets of information listed -- whether it be home and cell numbers or a cell number and e-mail address. To complete your transaction, tap the Done button in the upper-right corner. When you return to your contacts list, you'll see only one entry where previously there were two.
Lastly, if you want to rid your contacts list of your Facebook friends, head back to Settings > Facebook and move the slider to Off for Contacts in the Allow These Apps to Use Your Account section.