Following is the code for adding user information in iPhone's Contact.
As I told you that i dont know anything about the vCard, but this code posted by malinois in their answer here might be of use:
ABAddressBookRef addressBook = ABAddressBookCreate(); // create address book record ABRecordRef person = ABPersonCreate(); // create a person NSString *phone = @"0123456789"; // the phone number to add //Phone number is a list of phone number, so create a multivalue ABMutableMultiValueRef phoneNumberMultiValue = ABMultiValueCreateMutable(kABPersonPhoneProperty); ABMultiValueAddValueAndLabel(phoneNumberMultiValue ,phone,kABPersonPhoneMobileLabel, NULL);ABRecordSetValue(person, kABPersonFirstNameProperty, @"FirstName" , nil); // first name of the new person ABRecordSetValue(person, kABPersonLastNameProperty, @"LastName", nil); // his last name ABRecordSetValue(person, kABPersonPhoneProperty, phoneNumberMultiValue, &anError); // set the phone number property ABAddressBookAddRecord(addressBook, person, nil); //add the new person to the recordABRecordRef group = ABGroupCreate(); //create a group ABRecordSetValue(group, kABGroupNameProperty,@"My Group", &error); // set group's name ABGroupAddMember(group, person, &error); // add the person to the group ABAddressBookAddRecord(addressBook, group, &error); // add the group ABAddressBookSave(addressBook, nil); //save the record CFRelease(person); // relase the ABRecordRef variable 