You can purchase a prepaid calling card that lets you call the U.S.

You can purchase a prepaid calling card that lets you call the U.S. from virtually any landline phone for significantly less than dialing forthwith from your hotel or using your cellular phone.
Global phone card, for example, is available internet (pennytalk.aitrk.com) or by phone at (888) 292-8036 before you leave. The card covers calls built from any phone in more than thirty countries.
Using the Long distance calling cards to the U.S. from Canada cost 1 cent a minute, while calls from United Mexican States and Europe cost as little as 2 cents a minute. But check for additional fees, like the 49-cent a call surcharge.