How long would you wait...

I call them on it. I give a respectable waiting time and if they are beyond it I tell them this. You made a x:xx appointment and you are now xx minutes late. My time is valuable, $150.00/hour and I don't appreciate your casual assumption that you are more important than me. This won't happen again!
They are not used to being talked to like that and it usually straightens things out.
But I have had my file flagged in more than one place.
You see I try to be respectful on this site but out in the world I am pretty much an asshole!
When your boat capsizes and your friend doesn't come home it changes your perspective a bit.
DR out-----------------