Sorry to hear of the problems you have been having betty02 but i agree 100% with everything VC has said! As you say you have tried to offer them half of what you (should) have paid in the first place and it is still not good enough for them, also lets get real here, do you really think they care about you!? like most dealers all they really care about is the cash in your pocket. How many times have you been to a dealers and they want to do everything they can to help you before you sign the contract, as soon as you sign it's instantly that little bit harder to get in touch with them each time. So simple, let those personal feelings go in this case, look out for number one and as many have said it's their mistake!!! I would be very similar to yourself to be honest, i would almost feel guilty about it but one thing i have leant is, don't! it won't get you anywhere.
I hope all gets sorted for you, with the extra cash in YOUR hand!!.