Who is the owner of the land?

Respected Sir, This is Sunny from Mumbai. In the year 2004 we buy an pagdi house from the owner name qadir and we had transfer the names to the bill,electrcity and other bill except water bill. There is a open space bathroom located outside the house which measure around 5 X 6 feet in which there is water tap and water meter is connected,the open space bathroom does not comes under the pagdi house law. The issue is that we cant able to transfer the names to the water bill of the new owner because the bmc is insisting us for the property card which does not exist. our neighbor has illegally occupied the open space bathroom and they are saying that the space belongs to them,in future they are going to sell the space to the builder,in the year 2012 they had sold their illegal 5 X 5 feet open space bathroom to the builder now they want to sell our open space bathroom. we had a water payment bill from the year 1960 and water meter is connected in the year 1960. can we claim the open space bathroom on the evidence of the water payment bill,water meter ?if yes then how to make a new property card...we have a sale deed but in the deed the previous owner has only mention that he had no objection in transfering water bill to the new owners,he has not mention about the open space bathroom..... need help...