I did not expect this..

Hello. I am a pathologist, working in Charlotte county, Florida. On 11/10, I returned my leased car to Mercedes Benz, Sarasota. I was very tempted to buy my car again in the Sarasota dealer that treated me with a lot of respect for 3 years. But comparing offers for a Mercedes R class, Janet Bryant Blum (from Mercedes Benz Crown Eurocars St Petersburg) was best. She assured me that Mercedes Benz would waive the balance from the lease as a reward for buying another Mercedes vehicle, saving me $2300. The Sarasota dealer didn't waive the entire leasing statement. We agreed, and on the same day, Ms Janet Bryant brought the car to my house. In person, she reassured me that Mercedes Benz was going to waive the balance of the lease and she took my end leasing stament that previously I faxed to her. On 11/12, I called your Financial Department to confirm my zero balance on the lease. I was told that I had to pay the balance because the dealer didn’t. I then called the dealership, and was told by the sales manager Jason Good, that Ms.Blum’s contract was terminated, and that he will not honor the deal. He refuses to put me in contact with her arguing confidentiality and hang up the phone. I left many messages on Mr Good and Ms.Blum's cell phones. No reply. Next day I visited the dealer with my wife, and Mr Good told us that he was not going to discuss any further detail about the deal. He called somebody that came to his office and told us to leave the building threatening to call the police. End of story!! I left this place very dissapointed. For 3 years I was treated with extraordinary kindness and respect in Mercedes, Sarasota. I love Mercedes cars, I can not believe that this kind of people are working for Mercedes Benz. Dealing with dishonest people is every car buyer’s nightmare. I did not expect that at Mercedes Benz. How should I proceed?