Your situations don't happen. The one I stated has happened each and every time I've not gotten what I rented and it mattered enough to make a comment. I get the car they give me and a refund. Every time. I'm sorry that they don't seem to do this for you, but this is definitely not a universal experience. If they offer me the car and the refund (and they always do), I will take it.
Cheers.
Well, of course you'd take it. Who wouldn't?
The question is if the rental agency, like AA, doesn't offer it?