law: Railways Act, 1989
  59 Communication between passengers and railway servant in
  
  charge of train.
  A railway administration shall provide and maintain in every
  
  train carrying passengers, such efficient means of communication between the
  
  passengers and the railway servant in charge of the train as may be approved by
  
  the Central Government :
  Provided  that where the railway administration is
  
  satisfied that the means of communication provided in a train are being
  
  misused, it may cause such means to be disconnected in that train for such
  
  period as it thinks, fit.
  Provided  further that the Central Government may
  
  specify the circumstances under which a railway administration may be exempted
  
  from providing such means of communication in any train.