Gratuity claim refused by employer

Just file the suit in the  court.

File a petition to the controlling Authority in Labour department, since you are eligible for gratuit. service of 4 years and 11 months is eligible for gratuity enventhough resigned.

You should contest the matter before the controlling Authority.For eligibility Act requires 5 years contineous service.The definition of contineous service makes it clear that if during the fifth year  you have served for more than 240 days,it would be one year contineous service.Therefore it appears that you have completed 5 years contineous service and hence entitled to gratuity.