DDA — unable to get certified copies of allotment letter and possession letter

Address: New Delhi, Delhi

Website: Dda

I have applied for certified copies of allotment letter and possession letter for my house in mayur vihar phase 1, delhi alloted to my father in 1980-81.
Inspite of depositing full payment along with required documents, i have not received the same even after 4 months. My file is not traceable in dda records and dda is not replying to my rti application.