HDFC Bank — no 4k cashback for apple 5 series watch since 120+ days

I purchased a apple 5 series watch on 19th feb '20 using my hdfc card which provided a 4000 cashback within 120days via 6 months no cost emi option. It's been more than 120 days and the cashback has not yet been credited.
Secondly, the first month's emi has reduced 500 rupees more than the normal amount which should be deducted, i'm not sure why as my account had enough money for the transaction.
Been trying to reach the cc, and the call gets auto disconnected after awhile without reaching any personal.