Help: HDFC is not issuing amazon voucher even after applying for regalia fist card as per conditions

I did not receive 2000 rs amazon coupon.
I clicked on the advertisement banner in netbanking “offers” section. Banner said “Get 2000rs amazon coupon within 90 days of applying credit card. Offer is valid only if you apply through click on the banner”
as per the offer minimum 3 transactions within first 30 days of card setup then the entire value of the Gift Voucher will be shared to the elible account within 60 days of completing the 3 transactions on his/her registered Mobile Number/Email ID.
I have done more than 3 transactions within 30 days of card setup. So I am eligible for the voucher.
But I did not receive voucher on my mobile or email.
Its been more than 120 days now.

I am sending email to [email protected] every week but they are just saying they’ll let me know.
How can I escalate this?