Before you go off on your holiday shopping spree and get yourself a new wireless carrier as an early Christmas present for yourself, there are a number of things you need to be aware of.

What is number portability?
Number portability or WLNP (Wirelesss Local Number Portability) means that you can switch wireless services in the same geographic location and keep your existing phone number. It's pretty the much the same as keeping your wireline (i.e., hard-wired phone that plugs into your wall) number when you change local carriers.

Speaking of wireline numbers, in most cases, you'll also be able to switch from a wireline carrier to a wireless carrier, or vice versa and keep you phone number! I know a lot of people who are doing this; cutting the cord and just going wireless for their main phone number.

Is number portability available nationwide?
As of November 24, 2003, WLNP is available in the top 100 Metropolitan Statistical Areas (MSAs). MSAs are defined by the United States Census Bureau. You can get a map as well as a full listing of the Top 100 MSAs at http://www.fcc.gov/cgb/consumerfacts/wirelessportability.html#100msas.

If you live outside of the top 100 MSAs, wireless carriers have up to six months to comply with WLNP. So, no matter where you live in the U.S., you'll be able to move carriers and keep your number within six months.

The hidden costs of switching carriers
Be aware of the hidden costs if you want to switch carriers. Probably the best time to switch carriers is when your existing contract ends -- only now you can take your number with you.

If you're with a wireless carrier at the moment, chances are you have some sort of contract that ranges from one to two years. Just because you can now take your number with you, this does not mean you can simply break your contract to switch carriers. It's still costly to do so, with carriers charging anywhere from $150-$250 just so you can get out of your contract and switch to another carrier.