If you've struggled with getting your carrier to unlock your phone so that you can easily travel abroad -- or, gasp, switch providers -- today is an important day. As promised, seven US networks (AT&T, Bluegrass Cellular, Cellcom, Sprint, T-Mobile, US Cellular and Verizon) are now honoring a voluntary code of conduct that, among other things, lets you get your phone unlocked without a big fight. As a rule, carriers will agree to derestrict your phone after you've paid off your device or service contract. You'll have to ask most of them to do it, which could take up to two days. It's easier on a couple of carriers, however. Sprint will automatically unlock SIM-based cellular service on phones bought from today onward, while T-Mobile bundles an app with newer phones that lets you start the process yourself.