Depending on the social media platform, your strategy will vary. Doing what is right by the customer is always the best way to manage these issues. You always want to make the customer happy. Upon reading this you likely have a problem, but in the future it is best to satisfy your customer before they get to the posting phase of doing business with you.
In general you will want to follow these steps to deal with a bad customer review.
If the claim if false, vulgar or inappropriate you will want to contact Yelp, Facebook, Google or whomever controls the platform of the post for resolution. Our first advice here is to try your best to work with them. DO NOT get into a fire fight with these companies. This will not work out. Persistence and understanding will be your best tools with them. If that doesn't work, contact us and we will see what we can do. There is no sure solution in these situations, but the majority can be remedied.