Recharge cards are most often used in local sim cards,now you can hack this cards for free recharge.this trick can be probably used in all networks.
how it works? this trick can be used in followingway.
Buy two 10rs cards of any networks and scratch the card to see the number.some times you may get different number and some times you may find only the last three or four digits of the both the card may be different and the remaining numbers will be same,it means that both the recharge coupons are from same serial number,so this helps you to hack free recharge. first recharge with the number what you have and then see the last three or four digits of the coupons and if you find only that four digits are different and just generate some other numbers of your own which should be nearly next to the number which have recharged if you have correctly generate the next number from the coupon code you have then you use free recharge.
supported recharge coupons:
note:this trick i have tried only once and found working for me for only one time.