Generally it takes 3-5 business days to process refunds. If refunds could be processed instantly Jupiter’s credit/debit card could be used as a preferred mode of payment.
The process inherently takes long time. Any contested debit card transaction in an ATM is sent to the HO level of the bank which owns the ATM, then HO to it’s respective branch, then branch verify the ATM log manually, recommends and do the rectification. Further, often there are issues at NPCI’s end time to time, high failures in IMPS… many of it is not in the bank’s hand.