Storage Costs

I currently use a Cassoa gold site to store my van,this year they have increased the cost of storage,asking for the dimensions of my van,After a quick call to the site they explaned to me that because new vans are getting larger they have to charge more,so now i have to pay the cost of a twin axle when i only own a single axle due to the length of my van even though my van is not as wide as a twin.