How do I change a Title Poster that I don't like?

Some other person has put a project poster of my film up on IMDB. I don't like the poster and I am the owner of the film and want to put a different poster up. =On every other project of mine there is an option to ADD or Delete the poster but this one film doesn't let me. Any idea how I can delete and add another poster as the poster representing that title? Thank you.