I need some car help(huge vent)?

[random name]

October 31, my parents and I went to Michael's Toyota Dealership and bought a 2010 Corolla S. When we were waiting for the finance person, our dealer person started advertising all these accessories we could get for our car. He was describing these backup cameras you put on the side mirrors, and when you put the car in reverse, the mirrors would automatically change to the scene on the back of the car. This would be useful since I'm a new driver, and this is a new car I'd be practicing on. So we got that and the backup sensor that beeps when you're backing up the car. Now yesterday, my mom took the car to the dealership for our installation appointment. We got the car back this morning, and found out that we didn't get what we thought we paid for. The backup camera wasn't it at all! It was a freaking compass. So we went back to the dealership and talked to the manager since our dealer isn't there today. He prints out this stack of papers that shows our deal and says that no, we did not actually pay for a backup camera at all. We were fuming. These two things together costs more than a thousand bucks, and we're making monthly payments on this. We do not want to pay for something we are not going to use. Oh I am so sure that our 3 pairs of ears could not have heard the dealer wrong. He explicitly described the backup camera to us and told us that was what we were getting. I am just fuming over here. The manager says he will have a talk with our dealer and call me back tomorrow. So I might go back there tomorrow. What should I do? I asked him if I could just uninstall the service and get my $600 back, and he says no it's not possible. WELL, mister, that is NOT what I had paid for!!! Please tell me is there ANYthing I can do? *sorry for such a long rant*
Ha, no we can't just take the entire car back and demand for our money back. As soon as the car leaves their parking lot, its price depreciates just about half. >.<