Hi,
As you said, I would like clear first thing is that, No any employer can allow to work to any employee on National Holiday Without any prior permission of Shops & establishment inspector or Factory inspector with satisfactory reason.,
In case if they have take approval on same, so, they have to give the Compensatory Off against that day & also, they have to pay the salary or wage of that day on double rate basis.
Most of the employers are not ware that, without inspector permission, they can't do any thing against law. nonavailability of knowledge, they follow their own law or rules & regulation.
In my carrier i saw many of cases like this, most of the organization are not following the same, their director or owner is pressuring to do the monopoly.
So, in your case, you are eligible to get the compensatory off against that day & also get the wage or salary of that day on double rate.
i hope you will be satify with this information, in case doubt you can reply me or refere the Shops & Establishement Act. for more knowledge.