The drawback: using a local SIM card means you won't be able to use your own number, so you'll need to let your contacts know - or set your phone to forward all calls to the new number, a move that could trigger high call fees if your regular home-based plan doesn't include international calling. Also, family or friends calling you from the States will be charged for an international call.

WI-FI FOR CALLING HOME

If you have access to Wi-Fi, use Skype (skype.com) or another Internet telephone service like Truphone (truphone.com), which allow users to make free calls over the Internet to anyone who also has downloaded the service. Both offer apps for calls on your smartphone, so you don't have to be traveling with a laptop to use the service.

If you want to make calls over the Internet to people who don't use Skype or Truphone, you can pay as you go (expect to pay 2 or 3 cents a minute) or sign up for monthly plans to make unlimited calls in certain countries for a flat fee: $13.99 a month for Skype calls to land lines and mobile phones in more than 40 countries, or $12.95 a month for calls to landlines in 35 countries and mobile phones in 9 countries with TruUnlimited.

Skype also offers a free app for video calling on newer iPhone and Android devices with front-facing cameras, so you can have free face-to-face conversations.

Viber (viber. com) is another application for iPhone and Android phones that lets you make free phone calls and send text messages over Wi-Fi to anyone who also has the application installed. For a list of more than 500,000 free and paid Wi-Fi locations around the world go to Jiwire.com.

DON'T GET CAUGHT ROAMING

On a recent trip to London, Dan Keller, president of a medical writing and audio/video firm in Glenside, Pa., accidentally dialed a number on his contact list, probably as a result of the keypad being pushed inadvertently while the phone was in his pocket. While that number showed up only once in his phone's call log, he was billed for 13 calls, all 1 or 2 minutes each - which came to a total of $46 in roaming fees. "I called T-Mobile and told them my phone showed that only the first call was correct. They said I must have called it all those times," Mr. Keller said. The lesson: Be sure to lock your keypad to avoid inadvertent pocket-dialing.

For good measure, turn off data roaming on your smartphone to block e-mail, browsing, downloads and apps. If you don't, your bill can quickly skyrocket.