I was an early adaptor of Vonage:

Quote:

To place a call to an international location, use the following dialing instructions. From U.S. phone number to Canada: 1 + area code + number From U.S. phone number to Puerto Rico, Bermuda, and other territories: 1 + area code + number From U.S. phone number to other locations: 011 + country code + area code + number

For calls within the United States the 1+ is not used or the 1+ is ignored ..