First of all determine:
--- the company is registered as: Commercial or Industrial? And covered by which enactment e.g. Shops & Estbs Act, Factory Act and whether standing order (Model/Certified) apply and cover your designation?
---You are covered by the def. of 'Employee' as in Shops & Estbs Act , as 'Workman' as in ID Act (and Model Standing orders)?
---Your designation is covered by Certified stranding orders if standing orders apply does it cover your designation?
---What are your work hours mentioned in appointment letter or any other document applicable to you?
---Whether any of these enactments and also appointment letter and any rules/policy/employee handbook provide for Night Shift allowance?
Has it been paid to you in any month or any one else in same designation any time?
Thereafter you may relate your entitlement.
You may seek help of employee's/trade union leaders, labor law consultant,Inspector appointed under the above mentioned enactments.....
YOu may go thru:
Supreme Court of India
Bharat Electronics Limited, ... vs Industrial Tribunal, ... on 15 March, 1990
ttp://indiankanoon.org/doc/1800222/?type=print