Cleartrip — Cleartrip coupons

We ( wife and I) had purchased a couple of tickets from Bangalore to Calcutta using Cleartrip.com portal. While purchasing the tickets, we used the cleartrip coupons that we had received from HDFC for this trip. The problem was that we the coupon amount was not deducted from the total amount.
We then tried calling the customer care center, and the only response we got was that apparently we had not entered the coupon code. They refused to give us any cash back for this trip. We would never be using clear trip again