My iPhone 3G always shows an Unknown number calling when I've got that person's contacts, What should I do?

Question

When someone calls me, my iPhone 3G keeps on showing that it's an unknown number calling when I've got that person in my contacts.
What can I do to solve this? Thanks.

Answer 1

Simmilar issue here!
Summary: Incoming calls show up only as phone numbers, not with the caller's name.
Steps to Reproduce:
1) On your iPhone, save a person's phone number in Contacts with the country's dialing code in front (+ZZZ-XX-YYYYYYY, where +ZZZ is the country code, XX is the carrier, YYYYYYY is the person's phone number);
2) Make a call from that person's device/number to your iPhone;
3) On your iPhone, while ringing, shows the above number without +ZZZ and without the person's name.
Expected Results: No matter how the number is saved (as +ZZZ-XX-YYYYYYY or simply as XX-YYYYYYY) the caller ID should always show up, as in previous iOS editions.
Actual Results: Caller ID does not work as expected and as in previous iOS versions.
Notes: When I receive voice calls, the number comes in without the country dialing code in front, simply appears as XX-YYYYYYY (where the XX is the carrier code and YY is the number) and the caller's name does not appear. In my address book ALL my contact's telephone numbers are preceded with the corresponding country dialing code, because i travel a lot. If I delete the country code from a contact's phone number, and that number calls me, then the person's name appears. I'm am in Angola (country code +244) using iPhone 4, iOS 5, carrier: UNITEL (92)
On the other hand, SMS's are OK, i.e. the Caller ID is linked to the phone number and shows up (because SMS's are receiver with the country dialing code in front of the phone number, p.ex. +244-XX-YYYYYYY).
It has something to do with the Carrier Settings Update as in iTunes i get the error message 1630 which states that: "iTunes could not check for un update to the carrier for your iPhone. An unknown error occured (1630)."
Thanks