There are many customer satisfaction surveys conducted by thousands of companies each year. Some are more reliable than others.
The main difference is before and after. For example, in an election voters in an exit poll (Who did you vote for?) give more reliable answers than voters give before an election (Who will you vote for?).
THE NET PROMOTER SCORE (NPS) is a before question. The NPS is widely used to predict corporate growth by asking this question:
How likely is it that you would recommend our company/product/service to a friend or colleague?
THE WOMBAT QUESTION is an after question:
Have you told anyone yet through word of mouth about your satisfied customer experience with us?