Paytm — Doesn't get Cash Back

Order No.[protected] I used paytm application from my Microsoft Lumia 532 which having offer of getting cash back of 600 (per month 150) by paying bill using promo code lumia532. When I did the same, I doesn't get cash back. I called to customer care many times, but doesn't get assistance. Now this feels me harassment by not offering what they promised. Requesting to resolve this problem as soon as possible. Himanshu #[protected]