It can’t be done. ZDNet tried, with predictable results. The bottom line is that Apple has instituted a limit — you can only buy two iPhones. And they’re using your name and credit card number to enforce that limit. It’s their answer to the unlocked iPhone issue.
You don’t have to be a rocket scientist to connect the dots. Apple has relationships that its contractually bound to protect and must do whatever it can to eliminate the gray market. As far as unique indentifiers go, credit cards are a pretty good token for authenticating someone’s identity. At the very least, Apple is probably retrieving (from the credit card) and keeping the name of every person who buys an iPhone. This way, when you go to buy another one, they can see if an iPhone has already been purchased by someone with the same name. But then comes the question of whether they are retaining your credit card number as well. How could they not?
After all, there are lots of people with the same name and the odds are pretty good that certain names have already exceeded their quotas. But certain names coupled with certain credit card numbers. No way. The credit card number is quite unique and if Apple’s database shows that two iPhones have already been purchased by someone who’s identity was authenticated with the same credit card, that would be a red flag against selling them a third phone.