easy way is to sit in the car .. then they cant tow it away .. or even have a dog in the car .
i know someone who got a tool kit and took half his car apart to remove the clamp , left it undamaged took a photo to cover himself and then foned em to get em to collect the clamp .. they tried to get him done for damage .. but they couldnt prove any damage had been caused...

they are complete tossers tho .. think they are some sort of hero's