Double maintenance charges for single flat with 2 registrations

Hello, I have recently purchased a 3 BHK resale flat in Bhandup, Mumbai. The flat is one but has 2 registrations - 504 & 505 with total carpet area divided equally among both the flat registrations. Each flat has separate Share certificate with single occupants. As of now the society is providing all these flat owners 2 maintenance bills for each flat which seems to be correct, but all the additional contributions such as Cultural activities (Rs. 300) / Water Tank repair charges (Rs. 2000) and all such costs are also getting duplicated. This means that these costs are reflected in both my maintenance bills and hence have to pay double every time. All my Utility bills such as MSEB, MGL all considers this flat as one, but society still charges us on both the flats. There are around 80 flats with dual registrations and all have been requesting the society to make the contribution as one instead of 2 contributions. So wanted to check whether it is legally right for the society in charging us double contributions just because we have 2 registered flats with single occupancy? With regards, Devassy K