PhoneCardSmile is the international lowest cost leader for prepaid calling cards and phone cards. They offer many great deals for all around the world calling and you can save a lot of money. There are several cards designed just for internetional use. The best rates will really depend in the Country you plan to call,as the rates will differ.
International calling cards are the best options. International calling charges can be very high for US cell phones.
The best option when traveling would be a good blackberry, with international calling.
Ther are many international calling cards out there. I have found that Titan and Aries offer pretty good rates if you are calling Europe,about one cent a minute on a land line.
I would imagine this would depend on where you are calling. I would recommend SpeedyPin.com, an online calling card retailer that seems to accomodate calling cards to most countries. They conveniently list their rates on their main page.
There are many great locations to buy international calling cards from. I would recommend a specialty store that specializes in foreign good/foods. I would recommend an African or Mexican food store. Some of them can be really small and hard to find but usually have a great selection of calling cards.
International calling cards can be expensive. You may want to ask your cellular provider to add the feature to your phone. It is cheaper that way. If you still insist on purchasing cards you can visit Radio Shack, Staples and Best Buy.
It is difficult to determine which company offers the best and lowest rates on the international calling cards, however, a general consensus seems to be you should not pay more than $0.10 cents per minute.
When making international calls to China, the best calling card to use would be one that offers competitive rates, reliable connection quality, and good customer service. It is recommended to compare different calling cards to find one that meets your specific needs and budget.
There are many websites that offer to sell calling cards. One would be able to find calling cards for sale on websites such as Best Buy, Radio Shack, or Pingo.
The Best Cheap way of calling international to Pakistan is through toolani.com, planet-talk.co.uk/call-pakistan.aspx
You can find Deal cards here at http://www.pingo.com/en/landing/callingcard.do There is a lot of calling cards available for you I hope that you find one.