How do I lower the ranking of Negative comments?

Hello. I own a hair website and have been in business for 3 years. What I have notice is that the 1% of our unsatisfied customer take to the forums to trash our company name. They leave lies (most of the time) bashing our company. Most are posted on complaint forums, rip off report, etc. Most

I was wondering is there any possible way to lower the ranking of these reviews and boost our positive reviews?