Paytm Mobile Solutions — paytm cash rs.18 on parle bakesmith biscuit

Unable to redeem coupon of rs.18 cash on parle bakesmith biscuits
When i am entering the promocode printed inside the cover of parle bakesmith marie it is displaying that - invalid coupon code, enter valid code but it was a sealed pack and purchased from reliance fresh. Reply to complaint from parle received as forward complaint to [protected]@paytmmall.com which is not being delivered to paytm even after 2-3 attempts. Who is cheating to customers? Is it parle or paytm. Resolve the issue.