I went back to %APPDATA%\Microsoft\Network\Connections\Pbk\
%APPDATA% points to my user folders.
C:\>set app
APPDATA=C:\Users\Dave\AppData\Roaming
If your task is running as the system account, then I'm not sure what folder that will get resolved to. Do you copy the phonebook somewhere? You might have to use the /PHONEBOOK:phonebookfile switch.
If the task is running at startup, then maybe you need add in a delay to let the network fully initialize before trying to initialize the VPN. Verify that the phonebook exists and contains your entry.
@echo %date% %time% Task starting.
@timeout /t 30 > nul
@echo %date% %time% Finished with startup delay.
@echo.
dir %APPDATA%\Microsoft\Network\Connections\Pbk\
@echo.
@echo.
type %APPDATA%\Microsoft\Network\Connections\Pbk\rasphone.pbk
@echo.
@echo.
@echo %date% %time% Calling rasdial.
C:\Windows\System32\rasdial.exe "Linkso VPN"
@echo %date% %time% Task ending. Result = %errorlevel%