Help please anyone?

We have a problem with a Florida based business called Alexis Malcolm Kilts, who have been using our copyright images without permission. I first contacted them months ago requesting the images are removed. But they have completely ignored our requests, despite this being a clear case of illegality.

I find it very disturbing that an apparently reputable business would behave so badly, stealing our work and presenting it as their own. And whilst it is always possible that it is an innocent mistake due to ignorance or malpractice by some subcontractor, I'm pretty outraged that they have just ignored the complaint when taken directly to their main contact address.

Does anyone know the people involved? My next step with clearly dodgy companies is normally to go directly to their Internet Service Provider to have their site taken offline until the stolen property is removed. This is routinely done as they are in breach of their ISP's T&C by using other people's Intellectual Property without permission. But I don't want to create a problem if there is some innocent explanation such as long term illness or something. Anyone have any insider knowledge?