What do you do if you learn that your company's top executives are cheating your clients or customers?

This is a question of corporate governance and the answer to this questions can be relative in many situations, countries, nature of incorporation of company, etc. An attempt at going for the throat of top bosses - even if you have proofs - can land you in trouble if you are living in a country where democracy doesn't exist, the governance structure revolves round privileged nepotistic policies and where the company is trained to interpret your honesty through your colour, your nationality, the language you speak....and even your gender and the level of your job! In countries where public limited companies respect an employee and documented proof - and where democracy exists - you may write to the Board Chairman and complain with proofs. Doing that in an undemocratic set up  could be suicidal............you may .lose your job and may also be jailed through the influence of  corrupt bosses! Nonetheless, in  both democratic and  nondemocratic corporate culture, such companies would soon go out of  business whether you blow the whistle or not!