Society building Repair work

Hello Sir, We are from Mulund Mumbai, we need your help to understand certain issue we are facing in our society, about water leakage on external wall of our house due to rotting up small pipe, which exist within the wall, but it connects to water tap inside washbasin of our kitchen platform. I will be great full if you could give me your advice. An year before secretary of our society approached us with the problem of this leakage, & forced us to let the plumber do the work on the repairing of this leakage from inside of our house He didn't give us a clear Idea about who would be paying for this work, how much would be the cost, etc... He just advised us, to let the work happen & about the price & liability for that will be seen later And now I think it was our mistake that we kept faith on him & allowed to do the work, because later he handed over bill of the same work (Rs.4000/-) to us, which we didn't pay further, so he kept charging fine of Rs 150/- on it for every month. On this after two months we handed a later specifying how the work was forced to us & how it's external as leakage being from outside, pipe caused leakage, was in middle of the wall, & we never done any change or modification in that span of work by any kind of construction or plumbing work. Since th construction of the building & society formed. But secretary never bothered to reply on our letter & kept sending the bill related to work along with increasing fine for every month. So kindly help us to know where we stand on this & if our side is as per law And what we should do to come out of this & how.