Also I doubt the Sam's calling card gives you detailed online billing which shows everything, allows you to recharge your PIN online, allows you to skip entering in your PIN, you have to buy a physical card instead of getting it online in your underwear, and I doubt Sam's can beat BigZoo.com's international rates.
There's a reason I'm a rabbid BigZoo supporter, it's saved me THOUSANDS (yes I have counted) of dollars I use it to call mostly international since my cell phone has long distance within the USA. Their rates to Canada, Australia, Asia, Europe, and other countries are freakin' awesome.