If the new rate was disclosed before you agreed, and you were completely aware of it, and you accepted the terms, then you have nothing to complain about.
It is not an "unfair" or an "abusive" practice as long as the customer was fully aware before committing to the new price and contracting an agreement.
HOWEVER, if the contract was made based upon last year's prices, and the customers thought they were agreeing to last years prices, and then after agreeing, signing on, it was THEN switched to a higher price without their knowledge until their first rent came due and THEN they found out the price was raised, then the practice is "deceptive" and in violation of the Dodd-Frank Act.
The Dodd-Frank Act addresses "Unfair, Deceptive, and Abusive" business practices. If this is the case, then tell them they are in violation of the Dodd-Frank act because their practices are considered deceptive because their attempt to advertise one thing and charge something else after the contract was complete falls under the "Deceptive" section of this federal law. They will look at you with a great big "Um, What?" Look it up: "Unfair, Deceptive, and Abusive practices." But it is a federal law.
But, here again, they can advertise one thing, but as long as they fully disclose the price change before you agree, there is absolutely nothing you can do. They are completely ligit then. On the other hand, if the did a 'switch and bait' then it's a violation of the Act. If the new price rate was disclosed before agreeing to the final purchase, and NOT after, then you just have to suck-it-up, or find another campground.
I just completed a course on this for my employment. Opened my eyes.
Look up "Unfair, Deceptive, and Abusive practices" with a Google Search.