Buckle in, go to court, and double-down on the fact that the public's opinion of actors is pretty damn fickle at the best of times - particularly if what you released was in fact based on someone you signed a valid contract with who just sounds similar.
Of course, this is all dependent on actually having a complete defense of course - you absolutely would not want to find Scarlett Johannsen voice samples in file folders associated with the Sky model if it went to court.