Even menial things take some level of paying attention and, when you are intending to intrude upon someone you should, just out of courtesy - PAY ATTENTION.
Make sure you have the right phone number - no need to intrude on someone who is busy, sleeping (shift workers keep strange hours), or dealing with some life emergency/tragedy. Listen for the person you are calling to answer the phone - don't just be hanging on to the phone babbling to people in the room.
It's not that hard…
oh, yeah, don't be chewing gum when you call someone - nobody wants that in their ear!
I get this
