Changing email of a contact in address book

Question

Hey guys,

I want to change the email of a contact in address book. my code is as follow. but somehow it doesnt work. do you know why?

- (BOOL)peoplePickerNavigationController:(ABPeoplePickerNavigationController *)peoplePicker
      shouldContinueAfterSelectingPerson:(ABRecordRef)person
 {
      CFErrorRef anError = NULL;
      ABMultiValueRef email = ABMultiValueCreateMutable(kABMultiStringPropertyType);
      NSString *personEmail = [conversationHistory getReceiver];
      ABRecordSetValue(person, kABPersonEmailProperty, email, &anError);
      CFRelease(email);
      [self dismissModalViewControllerAnimated:YES];
      return NO;
 }