Just found this calling card on the net.
It shows that it has some unlimited calls, like to China.
According to the description,
ABSOLUTELY NO REFUND OR EXCHANGE !!WHEN USING A TOLL FREE NUMBER FROM A PAY PHONE A $0.90 PER CALL SURCHARGE WILL APPLY. A WEEKLY MAINTENANCE FEE OF $0.79 WILL BE ASSESSED AFTER THE FIRST CALL.
If only $0.79 is charged per week for unlimited calling, it’s still a good deal. I wonder how reliable it is.