"That's when I learned that even when you think the guy on the other end of the phone is getting what you're saying, is best to make sure the message was clearly received so both of you can avoid wasting your time."
Many years ago I did a C+G course to be a YTS trainer. One of the exercises was to pair off and be given a set of various shaped wooden blocks. One had to build a shape/tower behind a screen then describe to the other how to build the same model. It certainly brought home the requirement to be very clear and explicit in your instructions and to then realise that someone else's interpretation of what you said can still be different to yours.