Appeal against Metro fine?

Hi I was travelling by Metro and I had forgot my ticket at home. Actually it was accidental I happen to travel by train expecting my ticket in purse but it wasn't. Unfortunately there was ticket checking on the next station. I kept explaining to Metro staff that I do have a ticket but not at that time. They collected my details and send me a fine of $175. I wan to appeal against it as I do have a ticket. Do any one has idea how can I evade the fine and how to send a request to Metro on this. Do they consider such incidents? Anyone with such incidents in past?