Such companies are governed by Shops & Estbs Act of the state. Standing Orders (Model/Certified ) may also be applicable.
Work Hrs:8/day & 48 Hrs/week, beyond which OT is applicable.
The Act may allow 10 hrs/day max and may have a cap on OT/month and then per Qtr and then per year.............................beyond which OT is not permissible for employer and can be penalized for violation.
You must download proof of having asked to and then having worked for more than 8/day & 48 Hrs/week.................and claim OT.
You may go thru: Shops & Estbs Act , and also Shops & Estbs Rules and various registers/forms prescribed in it. The employer has to record work hours,OT as per these registers and submit to Inspector, O/O Labor Commissioner. Falsification of record is offence.
Now there are many employee's unions for your sector and affilliated with Trade Unions and Trdae Unions are more than willing to embrace the employees from your trade.
You must consult an able Labor Law Consultant/Service Matters Lawyer/Law Firm dealing in Labor law matters with all docs on record ASAP and preferanly proceed under expert advise of your counsel.