For those who might complain about the dive destination, difficulty, or group, I strongly suggest discussing those when signing up for a dive. If you don't, then you have no right to complain. Even if you ask and are told of an intended itinerary, the operator has the unfettered right to change the itinerary and you are not entitled to your money back unless you have something in writing saying you are. Of course, if the operator changes itineraries unreasonably and repeatedly, it will lose customers and eventually go out of business.
If you sign up for a specific dive at a specific location, then you have the right to that dive absent unusual circumstances. If those circumstances develop, you probably are not entitled to your money back unless there is a writing saying you are. If you have any doubts, ask.
And, I believe that if someone asks for your certification card and you show a lower level than your actual level, you cannot legitimately complain if the operator places you with divers of a similar certification level. Of course, when the operator asks for your certification level, you could ask whether the level would matter to where you dive or to what group you may be assigned.
You'd be amazed what asking can accomplish.