You could go with a hidden camera - but these people are slick. I am pretty convinced everything they are doing is technically legal - and that is the sad part of this whole thing. They can get away with it because they are not breaking any laws.
They are completely unethical and lie to you - but there is little in writing that they give you that guarantees you a "free cruise". It is all double-talk and promises never meant to be kept.
Note - the cards usually say "complementary" and NOT "complimentary." The first means "additive" or "coordinated" the second means "free".