CHEAPER: MetroPCS, a cellphone company that targets low-income urban households, is cutting the price on its unlimited data service.

BUCKING THE TREND: The two largest cellphone companies, AT&T Inc. and Verizon Wireless, have stopped signing up customers on unlimited-data plans and are coaxing those who have them to move to limited-data plans.

WHAT'S BEHIND THIS: MetroPCS Communications Inc. has just activated a new fourth-generation, or "4G" data network, leaving it with some spare capacity. However, the speeds it offers are well below those of AT&T and Verizon.