What to do when someone gets on your account and does slander on it?

on another account i have - my husband has the information to be able to get on it. I don't ever really get on that account but to check the junk mail. But on 9/15/2010 He went on my account and did review for the business I work for and said bad things about it. I want to know if there is anything you can do to help me did it deleted.