Height encroachment in dda sfs flat by ground floor flat owner

Hi, I stay in a dda sfs flat compound in Dwarka, Delhi. My ground floor neighbor is renovating his flat and has unduly extended a front terrace in the front of the house (23x6 ft) and in the process of creating a slant over it they have increased the height of the terrace beyond the limits of their roof and our floor height-wise. We had proposed to be allowed to use the additional area created due to this construction and they claimed Rs 10 lacs from us for the same. Now I want either the right to use this additional space (especially because they have brought it to our floor level already) or they should decrease the height. This is a violation of DDA 's permissible encroachment requirements also. Though this is outside the floor area of my house and they have been done this construction in spite of our request to them to mind the height before the construction happened but they completely ignored our request. Please suggest now what we can do against them to get a speedy action against this issue. Thanks,