Possession of 5 marla double story house, khayaban amin

Asslamoalikum wr. Wb.

Dear members/gurus!
I had booked 5 marla double story house in n-block of khayaban-e-amin. Installments have completed since 2014 but i could not get possession and still diplomatic statements of khayaban-e-amin management are there. Please guide me for legal/amicable solution.

Jazaka allah.