"Et tu Brute!" - from the play Julius Caesar written by William Shakespeare - Actor, world famous dramatist and possibly a schoolmaster.
"Tricks and treachery are the practice of fools, that don't have brains enough to be honest." - Ben Franklin - One of the founding fathers of the United States of America, statesman, diplomat and inventor.
"Don't get mad, get even." - Robert Kennedy - United States Senator, USA Attorney General and war veteran: naval seaman during World War II.
Summary: Over the course of your career, eventually someone will do something bad to you. You will have two options, one will be to get back at them, the other to do not react emotionally. There is a big difference in what you do in business and your personal life. How you conduct your personal life is your own business. You may choose to get even or do nothing. In sales and business, how you handle a negative situation like a customer lying to you can have a fundamental consequences to your career. Instead of dwelling on how to get back at someone in business, you must take a deep breath and behave as muturely as possible, no matter how badly you feel. Usually, the solution is treat the situation as objectively as possible and manage it knowing now that you can't trust this person or customer. If this customer is critical to your business, you must continue to service them without emotion, knowing that at least now you know how far you can extend your trust.
Sales Tip: Before you take action or make a decision to do anything, ask yourself if there is upside or downside if you do it. Think about this carefully. You could be surprised about what you discover. Many times I or someone in the company comes up with a great strategy such as a clever way to land a customer. On the surface it seems brilliant. Upon looking at the potential ways the outcome could end up, you may be surprised to discover there is only downside to do it and the risk isn't worth it. On the other hand, if it passes this test, you may create a great opportunity. Strategies can sound absolutely brilliant. Whoever comes up with the idea may impress themselves and the people they are with. Don't let the appreciation for how smart an idea is distract you from asking yourself if it will work.