Link to the response and text:
http://support.apple.com/kb/TS2326
Symptoms
When receiving a phone call or message (SMS/MMS/iMessage), one or more of the following may occur:
■Does not match saved Contact with same mobile number.
■Received call or SMS while the sender is roaming on another carrier's network does not match saved Contact with same mobile number.
Resolution
Try the following basic troubleshooting steps, one at a time, to resolve the above symptoms:
1.Verify that you have the contact on your iPhone. Tap Phone > Contacts and locate the contact. Verify that the contact's phone number is listed.
2.Update to the latest version of iOS.
3.Change the language of your device and then change it back.
4.Try putting the phone number in the contact in international format by adding a plus sign, "+", and the country code before the mobile number in the contact.
5.If that does not solve the issue, try the following: ■Calls: Tap Phone > Recents. Tap the chevron next to the phone number, and then tap Add to Existing Contact. Locate the contact and add the number as "Other".
■Messages: Tap Message, select the message to view it, then tap Add to Contacts. Locate the contact and add the number as "Other".
Additional Information
If you are using using Verizon as your provider and iPhone displays the ten-digit number instead of the name of the other party, please follow these steps:
1.Dial *228 from your iPhone.
2.When prompted, select option 1.
3.When complete, you will hear a confirmation message.
4.Force the Contacts, Messages, and Phone applications to close using the following steps:
1.Ensure that you have recently opened the Contacts, Messages, and Phone applications.
2.From the Home screen, double-click the Home button to display the recently used apps.
3.Tap and hold the icon for the Contacts application until a red minus appears.
4.Tap the red minus to close the app.
5.Repeat the previous step for the Messages and Phone applications.
6.Tap the Home screen to return.
5.Turn iPhone off and then back on.