Godrej Interio — Product quality and refund issue

Address:

Narendrapur

I have purchased a product from Godrej Interio, Narendrapur on 4th March. They sent a defective product which identified by us as well as the engineer. As per them the replacement of the product will take 3-4 week. I had purchased the product for an urgent need, so I ask them to refund the amount and also adjust the coupon of Rs 4000 I used during the purchase. Godrej refused the same and only refund the net amount. They also not mentioned the coupon discount of Rs. 4000 in the invoice. When we asked for the same, they put a note below.

Now I want the coupon amount or equivalent product from Godrej Interio and the interest of the net amount from the date of purchase. Please help me to et the same. Attaching relevant documents.