Vodafone India — refund

Address:

Mumbai City, Maharashtra, 400098

I recharged my voda number with a rs 509 unlimited calls+ 1gb data per day validity 84 days. While i was making the payment the page crashed and i did not get any receipt. I recharged again with the same plan. Thereafter i got a msg that the amount has been deducted twice.
I called up voda customer service to refund one amount back as the recharge amount is same and the double recharge happened erroneously.
The cust service agent told me it cannot be done as the 2 nd recharge overrode the first one and is now in valid.
The two recharges have happened in a span of hardly 10 mins. Yet they refuse to refund the money or give a credit note.
They reiterate the same thing on call and email saying that refund not possible.