Zingoy.com - Gift voucher invalid

I have purchased *** Rs gift voucher from www.zingoy.com, *** Rs voucher was of shoppers stop and while describing the information they were showing that it can be used online and they have given me ** Rs cashback which can be used after voucher will be used on shoppers stop.
Order Id: #*******, but after delivery of the voucher I used it online for buying the items but it was showing an error. I contacted the Zingoy for the support they told that it can be used only offline which is written in terms and conditions. But they are cheating me as the information they provided me at the delivery of voucher at my mail address. It was clearly showing that I can use it online also for the same I send too many emails from * days but they are not replying to my emails. I request you to please see at your end help me to return my valuable money from Zingoy.