The Yelp ads are a scam, don't fall for there trap, don't even answer their emails, they will promise the world that they have a proven ROI, however as you see almost no positive feedback, don't get burnt like many have been, including me.
Tip for consumers: Stay away from doing business/advertising with Yelp. Their business strategy is to scam you, they are very similar to the people who call you and are demanding payments through gift cards.