Flipkart — Fraud by the delivery man

I ordered Iphone 12 mini from Flipkart on 2nd October, with exchange value of ₹5250 for my old device Poco F1. The product was delivered to me on 5th October, 2021. The delivery guy told me that the condition of my device was not up to the mark and he could only give me ₹3950 for my device. I paid the remaining amount and received my product. But when the invoice for my product was generated, it showed that the value that my old device was only ₹5250 and not ₹3950, and same was shown on the order page of the product as well. I informed flipkart about the issue and the customer executive told me that it might take a few days for the value to get updated and I should wait till then. But nothing happened and the value that is shown in the invoice is same till date. I called flipkart again and then the executive told me that the delivery service was not responding and I will get refund for the extra value I paid within 3 days. When I didn’t get the refund I contacted flipkart again and then again they told me to wait for three days and if I don’t get any solution, I can call them again and ask for the refund. I waited for 3 more days and after not getting any solution I contacted Flipkart once again to ask for the refund. But again the customer service executive denied to initiate the refund and wait for 3 more days that was until yesterday. But again I didn’t get any resolution of my issue. I have ordered devices with exchange from flipkart as well and the exchange value got updated immediately when it was decreased. I believe that Flipkart’s delivery executive has misappropriated with the value of my device and I am rightful to get the refund for the extra value that I paid.