RBL Bank — Discrepancy in Bill Amount

4th May I purchased an Air-Conditioner from the Amazon portal and paid through RBL Credit Card by selecting 3 months installments. This month I received the last statement and I was cross-checking the amount to be paid & actually paid and observed the discrepancy so tried to connect with the Customer Support Team to understand. Instead of solving the problem, All I face is BLAME-GAME. RBL CS team throwing everything on Amazon merchant and Amazon CS throwing everything on RBL Bank.

Tired of this, I need a proper elaboration on this issue. I hope you take it a bit seriously and explain it to me properly. I had attached all the necessary images related to billing.

When I purchased it from Amazon, I was seeing a total of ₹36, 936.83 (With the deduction of No Cost EMI Discount - ₹803.17) however when I summarise 3 EMIs Installment amounts (₹12, 579.99 + ₹12, 579.99 + ₹12, 580.02), I got ₹37, 740 which was ₹803.17 higher than What I have seen Total on Amazon.

My purchase had come with A No Cost EMI Discount then Why am I seeing a difference of ₹803.17?