Question

I’m adding a contact to the address book, so far it just contains the name and phone number.

The contact appears in the address book when I go to view it but the phone number isn’t present.

ABAddressBookRef adbk = ABAddressBookCreate(); 
ABRecordRef contact = ABPersonCreate(); 
CFErrorRef error = nil;
BOOL success = ABRecordSetValue(contact, kABPersonFirstNameProperty, @"f name", &error); 

ABMutableMultiValueRef phone = ABMultiValueCreateMutable(kABMultiStringPropertyType);
success = ABMultiValueAddValueAndLabel(phone,  @"123456789",kABPersonPhoneMainLabel, nil);
CFRelease(phone); 

success = ABAddressBookAddRecord(adbk, contact, &error);
success = ABAddressBookSave(adbk, &error); 
CFRelease(contact); 
CFRelease(adbk);

Tried replacing kABPersonPhoneMainLabel with for example kABPersonPhoneMobileLabel but it makes no difference.
Why is the name appearing but not the phone number?

Every function returns YES.

Answer 1

Looks like your forgetting to call ABRecordSetValue with the phone number. See snippet below.

ABMutableMultiValueRef multiPhone = ABMultiValueCreateMutable(kABMultiStringPropertyType);
ABMultiValueAddValueAndLabel(multiPhone, @"1-555-555-5555", kABPersonPhoneMainLabel, NULL);
ABMultiValueAddValueAndLabel(multiPhone, @"1-123-456-7890", kABPersonPhoneMobileLabel, NULL);            
ABMultiValueAddValueAndLabel(multiPhone, @"1-987-654-3210", kABOtherLabel, NULL);        
ABRecordSetValue(newPerson, kABPersonPhoneProperty, multiPhone,nil);
CFRelease(multiPhone);