If the comments that they are making are not true, then you may have a potential claim for defamation... especially since it's impacting your business.  If your contract had any provisions about interfering with your business operations, you may have some additional contractual remedies. Before you file either suit, have an attorney send them a demand letter requesting that they cease with the negative comments....sometimes this is all that is required.Aside from the legal aspect, you may need to hire a small public relations firm to help you overcome some of the negative aspects of the rants on Facebook.  The fee that you pay them would be part of the damages you would seek if you had to follow-up with an actual suit for defamation.