The complete message is:
Your call cannot be completed as dialed. Please check the number and try again.
NOTE: This message appears before Windows Messenger attempts to dial.
This behavior will occur if the telephone number of the user you are calling is incorrectly entered in Active Directory Users and Computers.
Windows Messenger requires a space between the country code and the remainder of the number. When entering a phone number, use a modified canonical form:
In North America, a valid number would look like +1 (123)4567890.
NOTE: Without the space character, Windows Messenger interprets the whole number as the country code.
NOTE: This same error will occur if the server cannot route to the Internet Protocol-Public Switch Telephone Network (IP-PSTN) gateway.
NOTE: The phone number must also be valid for your particular IP-PSTN gateway.