Airtel — money deducted for failed transaction and it was not refunded

Address:

Chennai, Tamil Nadu

I'm using airtel number [protected]. I recharged this number for rs. 400 using my airtel app unfortunately the transaction was failed so again i tried to recharge with the same amount rs.400, second time also the transaction was failed but the the amount 800 was deducted from my account for the failed transaction.
Then i spoke with the customer care, they told 7-10 working days the money will be refunded but 20 days has been completed till the money was no refunded. This is totally unfair. Refund my money as soon as possible