leakage issue from upper floor flat

I am facing leaking issue from top floor since last 14 years. Upper flat owners son agreed leaking issue several times in the past but refused to do the repair work in his flat . I have complained society secretary several times and taken acknowledgement for the last letter but did not give me action taken reply or copy of minutes where my issue is discussed. Now today small portion of ceiling fell. Again I went to secretary to inform the latest issue , instead of giving any sort of solution, she wanted to have her dinner at 7.40 pm. Above Flat owner is now asking for documentary evidence that leaking is from their flat . How do i proceed. I was told by the MBMC to take letter from society so that then proceed with my complaint . Here i am stuck since last two years