HDFC Bank — void sale refund

I was mistakenly charged 800/- at "kalpana bhargava educational and health" greater noida, delhi ncr. And the merchant has cancelled the transaction from his machine generating a receipt stating void sale dated 28/11/2018. As promised by the merchant the refund would be reflected in my account in 4 to 5 working day which has not happened yet.

Pfa