In Australia you would remove the image and tell them to go away and that you arn't paying and it would be the end of it. That might not work in your country though. In Australia damages are based on the damage the person suffered and an account of profits for the use of the image. So if you used someone's image to make a million bucks they would have a right to some money for that. If you use an image on your blog or something the damages would be pretty low. Not sure if the law works the same though in your country. In most countries copyright infringement is not a crime. It might be against the law in a civil sense but all someone can do is sue you for it. It's not like the police are going to come. That might not be the case in some countries though. I think there are some weird copyright laws in the USA where people get sued tens of thousands for copyright infringement over one song which cost a few dollars. That's absurd since the damages are a few dollars.