People looking to walk into an Apple retailer and buy an iPhone with cash will be out of luck. The company is now accepting only credit or debit card payments for the devices so they can track who purchases the phone, according to an employee at the Apple Store in New York's SoHo neighborhood.

The new policy is Apple's attempt to prevent people from purchasing and then unlocking and reselling iPhones, a situation that has been a problem for the company. Apple won't let anyone without a credit card or debit card in their name purchase iPhones, according to an unidentified Apple Store employee in a phone interview.

"We need to track the purchases of the iPhone [because] we have people buying the phones, unlocking the phones and selling them," she said.

A report by the Associated Press last week said Apple was limiting the purchases to two devices and allowing users to purchase them only with credit or debit cards. According to store employees, the two-device limit has always been in place, but the noncash policy is new.

Apple's public relations team did not respond to multiple requests for comment on the new policy. However, it's no secret the company is trying to stem the tide of unlocked and resold phones, now totaling about 250,000. Apple Chief Operating Officer Tim Cook mentioned that number last week in a quarterly results conference call as the difference between the number of handsets sold -- approximately 1.4 million -- and those actually connecting via AT&T Wireless, the iPhone's exclusive U.S. carrier.

If one analyst's estimate is correct, those unlocked phones are costing Apple millions of dollars. Piper Jaffrey analyst Gene Munster said that he believes Apple receives US$18 per iPhone per month from AT&T Wireless, based on iPhone-related revenue Apple reported in its latest quarterly earnings, totaling more than $4.5 million in lost revenue.