Paytm — Cheated by saying cashback on website

Address:	560093
Website:	paytm

Hi buyed Samsung phone in paytm order number[protected] where it was showing cash back of 18 percent.but after buying they are telling no promocode applied ..but when I provided screenshot on the same on same day they told they will process manually and give in 24 hrs..but I buyed on 12 November 2015..they repeatedly told next day even through mail and now telling they cant give cashback.they are cheating us ..I have all mail and screenshot for proof