Removing incorrect credits.

A general question. Every now and again, having watched a film, I am aware that an actor (usually quite well-known) in the "uncredited" section, doesn't actually appear. Am I right in assuming that said actor's credit is impossible to remove because, after all, it is my word against the person who added the credit?

I assume, this is an issue that IMDB would also be concerned about. Not too good having incorrect information on the database.

By the way, I am not a rank beginner as regards adding credits as I have added several thousand (hopefully all correct!!).