By Katie Marsal

Published: 11:00 AM EST

Apple last week stopped accepting cash for iPhone purchases and reinstated a two-per-person sales limit in an effort to curb the black market for unlocked versions of the touch-screen handset.

The new policy began Thursday, Apple spokeswoman Natalie Kerris told the Associated Press. Before then, there was no cash restriction and the purchase limit was five per person.

"Customer response to the iPhone has been off the charts, and limiting iPhone sales to two per customer helps us ensure that there are enough iPhones for people who are shopping for themselves or buying a gift," Kerris said. "We're requiring a credit or debit card for payment to discourage unauthorized resellers."

Since introducing iPhone on June 29th, Apple has sold over 1.4 million of the handsets, the company announced as part of its fiscal fourth quarter earnings last week. However, it estimated that approximately 250,000 of those iPhones were sold to buyers who intended to unlock them and then resell them for use on wireless networks other than AT&T.

The new sales restrictions are the latest moves by Apple in its game of cat and mouse with iPhone hackers. Last month, it released iPhone software update 1.1.1, which rendered unlocked iPhones effectively useless.