Maintance of private terrace with roof and room

I am from Guwahati Assam. Our Promoter and his relatives  has kept three flats with private terrace in all that three flats with roof and room in that terrace area may be those are illegal construction. But he is not paying the maintenance for those terrace area. When our society was formed he himself was the secretary and he fixed monthly maintenance on fixed basis whereas there is very much difference in square feets of each flats. We have Annual maintenance charges also which is based on square feet. which also he is only paying for the area of flat not for the area of private terrace. whereas lift maintenance is charged on floor basis means 1st floor resident have to pay less lift maintenance then 3rd floor resident. He is not providing me the documents of approved master plan .I filed RTI for the documents for that also he objected to public information officer.

so, what action I can take against that promoter on assam