PVR — Incorrect or incomplete information provided by Customer Support Agent

I applied my gift card previously and it was showing invalid so i entered it today for checking whether it is working or not but once i entered the gift card code it automatically booked the ticket without any confirmation and when i contacted the customer support agent and asked that can i get 100% refund instead of 75% so the agent said that they can't provide a 100% refund instead of saying that refund is not applicable on gift cards and my ticket also got cancelled and i didn't get any refund as well.So i want to register a comlain againt the wrong or incomplete information provided by pvr agent.