In case your transaction using debit/credit card for recharging your mobile gets failed, they do not refund money, but say that you got free credits in your freecharge account.
For example if you recharge with Rs. 1000, & then it gets failed, your credit card will not be refunded back with 1000, but it will stay in freecharge account as credits, which you can use for recharging again.
This makes sure that you will go back to them again and again as 2/5 times debit/credit card transactions fail and so your money gets stored in their freecharge account.