Generally when a business gets a complaint, only one, they can look the other way unless it is a very large client. Yet when they get two about the same perceived problem, then the businessperson ought to stop and consider the source of both complaints. Why is that you say; two complaints is not a lot really? True enough indeed, let me tell you why two complaints might actually be 40-60 complaints instead of the two that you actually heard about.
You see regarding the "only 2nd person to ever complain theory