Certified Car Bank SCAMMED me out of $500 Seattle Washington

SCAM: Certified car bank contacted me in the begining of 2014 guaranteeing me that they could sell my 2005 Mustang within 2 weeks for $16,500 all I had to do is render their services by paying them $500. I immediatly said, no thank you! I asked how he knew i was selling my car and he told my that his company finds people off of craigslist to call. So a few days go by and the person would not stop calling me. I listen to what he had to say. He said we have a buyer ready to purchase the car in the next 2 days. The sales person told me that he would put $200 of the $500 in to show good faith. All I needed to put down was $300. The sales person said I would have my money back by the end of the week. It was Wednesday at the time of the phone call. He also said that he guaranteed the sell of my car within the 2 weeks because he had 5 other buyers lined up if the first one did not work. After going against my better judgement I decieded to try it out. Big Shocker! I didn't here from the company for the first week. So, I called and got the run around time and time again. Every week I would called and every week I was told. "We are waitng on the papers to be accepted". After a month I was told the deal fall through. I asked about the other buyers and off course I got some dumb excuses. So I was told that everyone was now on the case to sale my 2005 Mustang and if I would take anything lower. I said if you can get $11,500 or better I guess I can deal with that. 3 months go by and not ONE phone call. So I call and get the run around from hell. I was cut off throughout the phone call and told remarks like. " Are you going to call the phone company and tell them they are stealing from you because your phone bill is high" I replied and said " I am paying for a service that I am benifiting from. You are taking my money and not providing me any services. Thats a SCAM!! Mr. Simms or Simmons was this persons last name. Now I went from $16500 plus the $300 I put towards the ???? to $11,500 Plus $300 to nothing. I have lost over $5500 for the sale of my car. I stopped posting it on Craigslist because I was contected and guaranteed the sale of my car by Certified Car Loan. This Scam owes me at least $300 and as much as $6000 due to the value of my car dropping. PLEASE HELP!!