Indigo Airlines - Refund not credited by indigo airline

I booked a ticket on **th May PNR/Booking Ref.: JK**GN for a trip from Dubai to Chandigarh dated **th June ****. I cancel the same ticket due to unavoidable circumstances on ** May **** almost one month from the date of the flight. I called upon on Indigo helpline number for cancellation of ticket and refund of the same in my account. But refund amount is not been credited in my account till date. I also mailed them several times. As per indigo airline mail reply, the refund will be credited within * to ** working days but didn't get a positive reply.
The account statement of my saving account is attached herewith for your reference. The **th May deduction in my account is clearly shown. The same debit card is been used for flight booking payment. Card No. xxxx-xxxx-xxxx-****