Make a FaceTime call using AppleScript
This'll do it. You can input a phone number in most normal formats. Can't say I've tried them all:

set phone_num to text returned of (display dialog "Input a phone number to call:" default answer "")
do shell script "open facetime://" &amp; quoted form of phone_num
tell application "System Events"
    repeat until (button "Call" of window 1 of application process "FaceTime" exists)
        delay 1
    end repeat
    click button "Call" of window 1 of application process "FaceTime"
end tell