Amazon.in - Cashback not received as promised

I have uploaded **** rupees in amazon pay and got a msg that i m elegible for **% cashback upto *** rupees on bill payment. I have written a mail to confirm it and was confirmed by email received from amazon on ** sep ** that i am elegible for *** rupees cashback on bill payment as cashload offer and not reqd any promo code for this. On ** sep i have done electricity bill layment for rupees **** for which i ambelegible for *** rupees as cashback but amazon give me ** rupees cashback. I have written a mail on the same day and received mail on the same day mentioning that the cash will be credited on ** of oct. After passing so many days they denying to give cashback and saying that i am elegible for only rupees ** as cashback, which is not understood because i have first confirm the cashback offer on ** of sep and done bill payment after confirmation from amazon. Please do the needful.