Shell illegally charging for parking suitland-silver hill Maryland

On May 21, 2013 at approximately 3:00pm, my vehicle had a malfunction which caused it to overheat. I looked around the parking spaces to see if there was any rules on psrking. There was one sign stating unauthorized vehicles are subject to be towed. My friend took s picture of it just in case of any discrepancies. I confronted the clerk about my situation in hope to seek authorization for a few hours. The clerk informed me that if I wanted to keep the vehicle overnight, I must pay him $20. I informed him that I will pay him if all of my option run out and I must have it sitting overnight. So I found options to retrieve the vehicle before sunset. My vehicle was then towed way before night time. I comfronted the clerk and he started screaming at me about $20 for overnight. He gave me authorization fot the day. Then he tows my vehicle because I did not want to leave it overnight and  pay him $20. Also there are no signs or policies on payments of that kind. I think I was taken advantage of because I look young to the clerks. But I am an United States soldier and unfortunately can't afford tow fees due to a lsrge family. Plus it is my main use of transportation. I have been wronged and now wish to seek restitution of some sort. I take this situation very seriously and urgent. Thank you.