I understand correctly that though you've managed to get a refund in the past through the NPCI, thus, it works, you don't have a prior experience of refund with Stake or any gambling site?
OP, Thamizan, do you mind to try to escalate the matter and get a refund through NPCI platform?
Yes, I got refund using this method but it's not from any merchant, but a person still it is same for the Merchants too.
The first 48 hours is the critical period and if the time frame is beyond 4 or 5 days then I doubt this method will work, we can try the bank customer support, but it's unlikely to help.