I have an ex-employee that is posting negative comments about my company all over the internet on review sites telling customers how things "really" work here. For example, we have a policy that our major accounts are given special treatment. He has posted "unless you have a big account you aren’t considered important". That’s not true. All of our customers are important, we just have a different set of standards for our major accounts. He is also talking about some incidents that happened with customers that we would prefer not to be made public. Is there anything I can do to get him to stop?