Auto-recharge automatically credits your Ringo account when your balance falls below a certain amount (typically $2). This ensures that you call never disconnects in the middle of a conversation. Auto-recharge works with the credit cards that you've added to your account.
With Auto-recharge, your credit card account is debited in the same way as if you were making a manual purchase. However, with Auto-recharge enabled, you don't need to approve each recharge.