Bigbasket.com — Regarding refund of my amount paid

Hi I recently bought items from Big Basket and it was COD. I did the payment through UPI and the scanner was given by the delivery guy and the payment was successful atmy end. After some time the customer executive calls and informs me that the payment is not reflected at our end and so pay using cash.
Although this was hard to believe, I believed them and made the payment through cash as it was promised that I would receive the amount in 4-7 banking working days to the original payment mode.
The payment was done on the 23rd of March and its 9th of April today, but still I'm yet to receive the refund. I contacted the customer service and they speak as a novice of this.
As I see there are multiple complaint about the same, I would like you to resolve this matter as soon as possible