HELP WITH YELP

Must people have heard of Yelp. It is a website where people post reviews of businesses. When you are looking for a business, you checkout their Yelp reviews. As a small business owner reviews are important. I had several good and one poor review on Yelp. For some reason ALL the positive reviews had been taken down and only the bad one remains. Truth is I do not know the client who posted the poor review. I did post a response. I have emailed Yelp to no avail. Maybe because I do not advertise on their site I am being punished? I recently had a client post a review. However, after 3 days Yelp removed the review. Again, I do not advertise with Yelp. Hmmmmm! Needless to say I am not happy with Yelp. You can not defend yourself. When positive reviews are written, Yelp takes them down. No wonder they face constant litigation