With the collaboration of irctc, Indian railways introduced a service for complaining about any problems in a running train. This is a great service for passengers and they can complaint on any problem related to the train.
How to complain
Passengers have to send sms to 8121281212 with the train number and exact problem in the train (like fans not running, water problem, sanitary problems in bathroom etc). As soon as passengers send an sms, indian railways will acknowledge the passengers and respond to the problem.