Go to the PGPORTAL website pgportal.gov.in, register yourself, and click on 'Lodge Your Grievance'. Choose 'Ministry of Railways (Railway Board)' in the drop box and shoot off! Try to provide maximum information, so they don't reject your request for flimsy reasons.
All the best!
PFA the reply I got from Western Railways in response to my request for starting PUNE-ST/BRC day time intercity train.