I dealt with the same Melissa during my signing, I thought she was the biggest con artist, with a major attitude problem. She also tried to convince me to get the gold package and kept trying to con me into getting it over and over! Whatever happened to customer service! I can't agree with you more, their whole behavior changed, the minute they got my check for the down payment. Guess, now that they had me on the hook, they didn't care. I wish to never go back there again, nor will I recommend that dealership to anyone.
I only wish that I had read your post earlier!
But, I do love my new altima...it's the only saving grace!