Gratuity denied

I worked for 4 years 271 days in Railways and resigned.

Now i claimed gratuity since 4.8 years is to be treated as 5 years for i.e. elilgible period for claiming gratuity under gratuity act.

But Railway Admn. rejected my claim quoting Rule 70(1)a of Railway Servant Pension Rule, 1993, which allows gratuity only on completion of 5 years qualifying service.

Pl guide me in this regard.  Whom to approach.  What is the remedy.