This is what you can do to enable block on an extension.
Go to the extension, click on PHONE TERMINAL SETUP
At the end, enable Password Protection, and enter your password.
once you click ok,
from your phone, dial *11, and enter your password.
This will now block the phone from any numbers being dialed out.
Now dial *11 again, then enter your password.
You have now unlocked your phone. You may dial out.