society maintainance charges

Hello, I am from Mumbai and have a flat in Mumbai itself which I have given on rent. I regularly pay the 10%non occupancy charges along with the maintainance fee usually in bulk in advance. However recently the society has started deducting rs.500 from all tenants who have given their flat on rent in the name of "welfare fund" without informing or taking consent. Our building is scheduled to go under redevelopment in 6-8months. When I questioned them, I was told that there is a provision in bye laws wherein those who have given their flat on rent should give some token amount to the society as a goodwill gesture. Please let me know if there is indeed any such provision under the bye laws. I am planning to file a police case or file a legal case against this society as they have been harassing me in every meeting and have already deducted the amount from the advance payment I had made. Please advise.