the labour rules says that the gratuity must be paid from 1/1/2005 (as per the new law) this is a must for any employee. the amount is 21days of current salary per year. so you should get from 2005 to date. if you have your contract with you than you can approach labour department. but i feel that you should have done this before your sponsorship changed. but still you can go to labour department to claim your rights.

good luck!