This is the "nuclear option" for call barring. It sends a command directly to your network provider to cancel restrictions.
Save that code in your contacts as "Unlock Phone." If you ever run into the "call barring" issue again, just dial it and hit send. call barring turn off
Before diving into the "how-to," it is important to understand what you are looking for. Call barring is a network service. It is distinct from "Blocking" a specific number. This is the "nuclear option" for call barring
Then press the button.