Amazon India — delivery not done for christmas

I have made a purchase for a christmas gift with a guaranteed delivery date of 25th dec 2019. They did not deliver and even refused to give a refund. They keep saying they are investigating but they never call back or give feedback on what’s the issue. As a customer they need to advice me a way forward either give a refund or make a delivery. You cannot keep a customer hanging. Calls to customer service and social media complaints only result in same text book responses.