The calling phone number may not match the contact name and therefore the name is not shown when you receive a call or SMS in the following situations:
- The phone number is defined twice in the People hub, the same number is found for two or more contacts (usually the last 6 numbers of the phone number are significant).
- The phone number is in a different format than the number received in the incoming call. The phone number may have been stored in the local format while the incoming call number is in the international format (including country prefix), or vice versa. The number may not properly match a contact name in this situation, depending on the device variant and the length of the calling number. In order to verify the correct format of the contact phone number (local or international), check the number which is shown when the call is received and edit the contact details accordingly.
If the problem persists, make sure your Nokia Lumia is running the latest software. For downloads and assistance, go to your local Nokia website.