Dialplan functionality
Currently, Zoiper 3 for Windows does not support Dialplan functionality.
To add prefixes to the numbers you are dialing you can use Windows Dialing rules.
You can edit Windows Dialing rules from:
Windows Control Panel/ Phone and modem options.
Windows replaces the + in the phone number with proper 0 or 00 depending on your current country/area code.
If you are in the same country/area + is simply stripped.
If 0 or 00 should be dialed always, then the number should be entered in the number itself.
Note: For the dialing rules to be applied, the phone number must be in cannonical format (start with + and it should work).
To enable Windows Dialing Rules support in Zoiper 3 open Settings menu -> Preferences -> Automation.