when you wake up saturday noon just to see your phone having 10 missed calls from the same unrecognized number, dial back and find it to be a mad client,
complaining about some graphic issues on a site you have nothing to do with.

checking the site; there is nothing wrong so you tell him to clear his browser cache.

he gets mad shouting a silly programmer shall not tell him what to do with his computer and its the site, not his browser.

i ask him if there is the same issue with another browser or computer..
he giggles a little then turn silent..

2mins or so later, he says: i'm gonna let your boss know about this then hangs up..

that client seems really quite unreasonable

Over time I've begun conditioning people to call me when I'm available and that's it. I started by never setting up voicemail. I've not had voicemail on my mobile phone for over 5 years and I'm still alive. The second thing you do is set up do not disturb at a time that reflects normal business hours. Basically anything after 5pm until 8am goes straight to my nonexistent voicemail. That filters out a lot of bullshit.

What happens next is really awesome. After missed calls lead to no option to leave a message, and if it goes straight to "no voicemail" a few times they think that they have the wrong number or they realize how much of a dick they are for repeated calls.

If they really need you they'll text or email. At that point you're in control of the conversation.