what actions can be taken for not providing occupation certificate?

Society was formed against the will of the builder before about 16 years in society only 7 floors / 7 family and ground floors shops / office builder has not handed over Occupation certificate as of today as he has added 5 more floors to the existing 7 story building though society has given permission to build 3 more floors onlyagainst payment of Handsome amount + car stack parking + etc which he has not done as of nowand not even paying property taxes / bills of elevator company / etc, society has filed law suit in National Forum meanwhile society was billing / collecting funds to maintain the society / payment prop taxes / etc, i have been gifted the flat from my brother and society has carried out endorsement in 2015, at that time all the dues were current, now society has come us with statement for taxes from day 1 ( even before the society was formed ) and asking me to pay the short payment from day 1 even i was not the owner, what are my rights ? can i defend myself ?