Paytm Mobile Solutions — Paytm cashback not given: promo code removed after order placement

Address:	Kanpur, Uttar Pradesh, 208010
Website:	paytm.com

I placed an order at 4:13 pm, may 21 2017 for lg 1.5 ton 3 star split ac (Js-q18spxd).
I paid rs, 41408 for the same which was eligible for rs. 5000 cashback.
I applied the promo code and waited for my order to be delivered.

But, to my surprise they delivered it after 10 days and no cashback after that.

I asked them, and now they denied that we have applied cashback promo code and now it is removed from orders section in website. They are tampering with the data.

They are not ready to return the product either. Rejected the return request and no cashback.
Same product is available for 38k in other websites but i went for paytm because of better deal, now i am at loss.

Paytm must give proper reasons for all this cheating they have done.