Delhi Development Authority [DDA] — No response of complain

Address: Gali n. 4 kishan colony

Respected sir,
I have written a complaint on 8th dec. about some elegal person are doing construction on dda land in kishan colony parladpur bangar near kali mata mandir.
But I did not find that there is any response of my complain. Those people are still doing construction on that site. If you are unable to stop this construction then please tell me the right authority to whom I should go for another complain.
Thanks