(MONEY Magazine) – Some 12 million cell-phone users are expected to switch carriers this year, now that a new law has made their numbers portable. That has the nation's largest carriers rolling out a steady stream of sweet deals.

Cingular, for instance, is offering 500 extra rollover minutes a year that subscribers can use to pad their monthly allotments. T-Mobile has extended its unlimited weekend calling period to include Friday. And Sprint PCS is now starting its free evening calling hours at 7 p.m. instead of 9 p.m.

Truth is, you probably don't even need to switch carriers to get a bargain in the current competitive environment--you can probably score a deal just by calling your current carrier and threatening to switch. "Consumers have a lot of leverage right now," says Sam Simon of the Telecommunications Research and Action Center. "Find out what offers are out there, and see if you can use them to get a better deal." --CYBELE WEISSER