Sorry that you've run into a business that gave you the hard sell making you believe that you were getting an incredible deal not to be missed by "buying now!"
I agree that you must review the company, but just state the facts - no name calling or opinions. Obviously you're steaming mad - who wouldn't be? I also believe in karma - so what goes around, comes around. If this company continues to do business in a deceptive way, word will get around about how slimy they are and customers will be less likely to do business with them.
As far as the BBB - you can report them, but they won't do anything. Businesses that are part of the BBB pay hefty membership fees to be listed on their roster. If you report them, the answer you'll get from them is "We'll place your complaint into their file." They'll use this information in case anyone calls in the future for a reference asking if any complaints were made against this company. As far as any recourse to your situation, the BBB is pretty benign.
I don't think that it's a good idea about making up a fake account and writing your review on Yelp - I always see others on the conversation threads touting the Yelp creedo "Real reviews, real people." So, you do that I find that hypocritical.
Walter, from what I can tell, you're a cool guy with great integrity. This is a hard dilemma as you want get justification for being duped without bodily harm. I know that your reviews carry weight here on Yelp - so, just state the truth and the facts and all will take care of itself.