Flipkart — Item showing as delivered but nothing has been received

I had placed the order for voltas ac on 11th of may and the same was expected to be delivered on 16th today. However, till 10.30 pm it was showing in transit and at 10.46 pm i received an email that the item has been delivered on 14th may at 11.59 pm.Since then, i have been calling on the customer support and didn't receive proper response. They have been asking me to wait till 21st may for reason of error in their system or if it has wrongly updated.This is a prepaid order & i don't have any tracking info.
All it is showing on the app is delivered, customer service is saying it is system error. This is highly disappointing and unexpected from Flipkart.