Snapping in a new card will make your phone act as if it's a local phone, complete with a local phone number and local rates.

FORBES: Magazine Article

Make sure that when you open a new credit card account, you read the disclosures they come with.

FORBES: Who's Paying All Those Credit Card Fees? New Users.

This means that if you purchase a local micro-SIM card (the ones compatible with the new iPad) you can make and receive phone calls on Skype or other VoIP service for about two cents a minute, in contrast to the high cost of roaming voice calls based upon all of the U.S. carriers pricing plans.

FORBES: Is The iPad Better Than A Cell Phone For Global Roaming?