OnePlus - OnePlus Cashback not processed

I placed an order on https://www.oneplus.in website for a OnePlus * Pro phone around **th October **:**am.

This was in reference to the American Express Offer mentioned here https://oneplussupport.s*.amazonaws.com/AMEX+T%**C+from+**th+oct+to+**rd+oct.pdf.

In the morning I see the same order dated as **th October instead of **th October and the same is being repeatedly mentioned through your Customer Care also.

On repeatedly pointing out, I was asked to reach out to the email support center with proof of the transaction happening on **th October only.

After following up for * months I got a response that this is not possible from their side, as the invoice date remains the same.

Order Details:
UserID: anirudh.mangipudi@gmail.com
Order Number: M******************