I just got off the phone with airbnb and you are exactly right, they changed it instead of cancelling it and I didn't know any better so I accepted it - my bad. I didn't want to decline because I was worried about getting a bad review.
I'm gonna chalk this one up to a learning experience and me knowing just enough to be dangerous sometimes lol - they were very nice people and I don't think they realized what they were doing.
I agree that they probably shouldn't allow guests to change it once they've checked in though. I seriously doubt I'll make up those two nights' rental.
Thank you for your input - I really appreciate the advice and assistance 🙂