Want to file defamation case but don't have offenders name or address

Some people write on facebook and forum website about me and my company that we are fraud and fake company any many more. how i will move to court to remove this content? , if i go to police then police said section 66A closed down and you have to move court under ipc 499,500, if we go to court the lawyer said u need name and address of offenders, without name and address we can submit the case. on facebook and forum site no name and address is available, so what we can do?