LittleApp — purchased voucher didn't work and money not refunded yet

Address:	New Delhi, Delhi, 110030
Website:	www.littleapp.in

On 24.05.2018 i purchased a coupon of pizza hut worth rs 500 on the app,
Which was not accepted by the merchant. The merchant said the coupon had 0 balance. And they said me to raise a ticket through the feedback section from your app, after which i got a reply saying "for the order pizza hut we validated the coupon & found that you have utilised the coupon & the balance is zero. Hence we will not be able to proceed the refund".

But the pizza hut guy didn't accept my rs 500 voucher.