Water Supply Disconnected And Access To The Roof Denied.

I am the owner of a floor of a residential block comprising of a total of 3 floors and a terrace. I am on the first floor. My water tank has always been on the roof of the building and there were no issues. Just yesterday I was called over the phone by the owners of the top floor who wanted a personal meeting. During the meeting I was told that I could no longer have access to the roof and that my water tank has been removed. They want me to create a new structure for my water tank away from the roof. During the discussion, I also found out that the owners on the top floor have illegally constructed rooms on the terrace of the building without and planning permission. The building is very old and form of additional construction on the roof is bound to jeopardize the safety of the residents below. The structure has become unsafe. I would like any suggestions in regards to what I can do in regards to 1. Access to the roof so I can reconnect my water tank. 2. Demolition of the extra construction on the terrace The property is based in GK1 of South Delhi. Thanks so much for taking time to answer this.