Illegal installation of ac by neighbour

Dear Members,

I am facing a serious problem these days due to my neighbour who is residing on the lower floor in the same building.

This property is owned by a lady who owns 2 flats on the same floor. Earlier, she and the other neighbour (on the same floor) had installed ac and placed the exhaust unit of their ac just outside their flats (please note that the wall where they have placed their ac is neither the terrace nor the road facing wall). Whenever they start their ac, the exhaust unit exhales hot air which in turn troubles my family as I am residing just one floor above. Now, that lady has installed one more AC just beneath the cross ventilation which is actually an Iron Jaal.  Now situation has become worse as now onwards whenever they start their ac, it will make my flat an oven. In summer, it will tough for us to stay. I am little worried for both of my parents as they both are older person.

We had a word with them in order to resolve this matter, and suggested her to place her AC on the terrace where other flats owner have place the exhaust unit of their ac. But that lady denied clearly.

Please suggest me the best way to resolve this problem as I am not aware of to whom I should file a complaint / who is the correct authority for this.

 Hope to get the best remedial action for this problem.

Best Regards.