Pratikar charge

Dear Sir/madam, I have bought flat in Noida Extension, the BB agreement was done in 2012 and still waiting for possession. builder is asking some "Pratikar Charges" to give it to Greater noida Authority which was not mentioned in BB agreement. Pratikar charges is for builders who got land from authority at cheaper price but later supreme court ruled to increase compensation to farmers. As per RTI, the charges were supposed to be paid before end of 2011. which is already paid by builder but now its being asked to buyers who bought flat in 2012 beyond. some groups from different Tower in same project filed petition in national Commission for Consumer court under Article 21and court asked groups to publish in news paper so if other people can join if they want to. however now builder is negotiating with those people. and they have stopped pursuing this case. I was wondering, can someone from different tower/same project be party of this petition? or do we need to file different petition using reference to this?