Flipkart — buy back guarantee of flipkart

Address:

D.NO. 9-13-107,, NEW RESAPUVANI PALEM,, OPP.SWARNA BHARATHI INDOOR STADIUM,, VISAKHAPATNAM-530013, Visakhapatnam, Andhra Pradesh, 530013

I am praveen i bought phone of realme2 pro on oct 2018 and i want to exchange my phone under buy back gurantee to realme3 pro on 20 june 2019,

The wishmaster has rejected my realme2 pro phone due to a small dot on the back of my phone and i am not able to exchange my phone.

So i want a strict action against wishmaster or flipkart in their unnecessary delay of my phone,
I have sent images to flipkart and again they are asking.