Internal leakage due to upper flat bathrooms

I am a resident of a Co-operative society in Thane, Mumbai and have been facing a very common and persistent concern of ceiling leakage/seepage due to the flat above me. Despite of multiple attempts to address this concern amicably with the owners and my housing society the issue has just been ignored and stalled by both parties. I have written more than one letter to our society office to mediate a dialogue and amicable resolution between us and the flat owners who reside above us, since clearly there is no intent on their part and we are unable to run around forever. I will highly appreciate if you can suggest any other ways to get a fair conclusion to this ailing issue of mine. The society has concluded that the leakage is due to an internal issue (upper floor bathroom), yet has never intervened as a mediator to urge any action from the occupants of upper flat. We are happy to bear part expenses but it seems neither the owners of the flat above nor the society is interested in even moving a single step to resolve this concern