Paytm — Pytam is Not providing me cashback offer of promocode that i applied against order no [protected]

Address:	Pune, Maharashtra
Website:	www.paytm.com

I have ordered e-O Adult Cat Food Chicken Veg 7 Kg on 22 sept 2015 with coupon code "Pet30" on www.paytm.com I did not get any cashback from paytm from promocode which gives 30% cashback in paytm wallet. When i logged a complaint at paytm, paytm executives are saying that i had not applied any promocode. I clearly remember thet i have applied promocode and i also re-verified that i have applied promocode for cashbak amount check. The only reason that i have purchased that product is due to promocode offer.and i checked i am getting 450 rs cashback and hence i purchased the product. What proof am i supposed to give to paytm to show them that i have applied promocode while giving order? Am i supposed to record every session while i place order with paytm?If so, please they should inform such notice publicly. Please help me get the benefit under the promocode that i have applied against order [protected] on paytm.