Changes in the wireless phone world are creating a strong market for used phones.
Mike Russell is thinking about switching to Verizon when they start offering Apple iPhones, but what will he do with his old iPhone from AT&T?
"I'm think about selling it," said Russell.
A number of retail stores from Radio Shack to Best Buy are offering buy back program for used phones.
Tom Tullie is CEO of ecoATM, a touch screen kiosk that pays for cell phones in a number of San Diego malls.
"Just like a used car market," says Tullie, "there's a market for used cell phones."
Tullie says as new generations of smart phones hit the market, owners want to upgrade, creating a large supply of used phones.
The company pays for the phones on the spot then sells them to wholesalers who put them on eBay or to foreign like China and India.
"Our society wants to keep trading up and trading up and this really give you a beautiful opportunity to put your phone in, sell it and go on to something else you want," say Tullie.
A used Apple iPhone 4 often sells for between $300 and $400.
Motorola Droid and BlackBerry phones are also popular on the secondary market.