Hyundai i10 Era — Discrepancy in Billing

Address:

Uttar Pradesh

I have purchased a Hyundai Car i10 from Nimbus Hyundai Noida. I made a payment of Rs 3,84,549. When retail invoice for the car purchase was given to me, The cost mentioned is 3,65,000. They are not ready to give me the total amount paid bill to me. They say we can give that to you in writing, it is Hyundai policy. When arguing on the same, they say we will give you the invoice with the exact amount paid but then you will have to pay the tax for difference amount.
I am not satisfied what they are telling me. I think Hyundai is not ready to bring the sales in Black and white and some discrepancy exists. I am interested in taking a legal action against them.
At the time of paying the amount no such clarification was given to me from NIMBUS HYundai. Now, when retail invoice has been given, the difference of 19000 they are not ready to justify.
The documents submitted are not in concurrence. Please help.
The Car has been purchased in the name of my Father Mr Rajendra Kumar Garg on 24.05.10