Amazon India — problem with cashback

Address:	Kannur, Kerala, 670694
Website:	www.amazon.in

I purchased oneplus 6 which cost ₹34999 on may 22, 2018 from amazon.in, i paid ₹1050 as oneplus 6 giftcard and rest 33949 inr through my sbi card, i received the product on may 25, 2018 and my order number is[protected].
At the time of purchase there was a cashback offer of ₹2000 with sbi card. It should be credited to card holders account on or before august 28, 2018 but i haven't got any till the date. I have contacted the amazon customer service for several times and they told me i'd get my money shortly. Last time when i contacted them to notice about the problem they told me that i'm not eligible for cash back because i haven't done the full payment through sbi card. But i have done my complete payment through same card and in the "amazon.in faq for oneplus 6 sbi cashback" section have "minimum transaction amount to avail cashback is ₹28000.
They are repeating the same things again and again, now i've fed up with amazon.in response.

I'm sending the proof of my mini statement copy, some chat screenshots with amazon customer service, oneplus 6 sbi card faq and my order summary.
Please check the attachments and kindly help me to get a proper response from amazon as soon as possible.