Maintainance of society in mumbai

We have just shifted and we have purchased the flat from person who had purchaes from builder. When purchased we have executed 2 agreement for 1 flat. We are staying in 38 storey building  which got OC in 2016, which has 8 flats on every floor  Series 1 = 3bhk 2 agreement  Series 2 = 3bhk 2 agreement  Series 3,8= 3bhk 1 agreement  Seires 4,7= 2bhk 1 agreement  Series 5,6=2bhk 1 agreement  Members who have purchased 1 and 2 series where shown single 3 bhk flat while booking the flat and while registration they executed 2 agreement saying that they will amalgate the flat after receiving the OC. If you see the house it will look unified 3 bhk house having single kitchen, single Mahanagar Gas pipe line, single water line  and he has provided 2 electric meter. All 72 flats are identical 3bhk and all the advetisemwnt on site you tube videos is of 3bhk. Now series 1 and series 2 is 3 bhk super built up 1627sq feet and series 3 and 8 is 1550 Sq feet. Series 3 and 8 maintenance is 10k and series 1 and 2 is coming 17500/=  Diff of sq ft is 77 and maintenance diff is 7500 now members of 1 and 2 are opposing this and asking society to charge per Sq feet basis. What will be the solution for this legally that 1 and 2  series pays in accordance to other series. In reality there is no 10 flats there are 8 flat only even in lobby the plan is showing 8 flats per floor. Even on name plate it is written 1201/1201A Society had formed fincom to submit the report they said if you want to consider 10 flats than they should get 2 parking 2 postal ballots   2 separate name flat. 2 water line ,2 gas line then we can count it as 2 flats. Then also some members are making havoc and they want to maintenance. All 72 flats are same 3 bhk you will not find single one bhk and 2 bhk flat in 1 and 2 series. So this game plan of builder and now secretary and treasurer are insisting on 2 maintenance. Guide me in this