From the other side of things
Many years ago, before everybody had mobile phones. I needed something from IT department. They never answered. But then I dialed 0 then full number to make it look like an external call. The call was answered immediately. I do not remember the rest but think I got what I needed after some complaints about calling her "private" number. At that time calls from outside where likely not work related.
I only now realise what risk I took.