I do not know where you are calling, but I have ditched calling cards for a service called Gorilla Mobile for International calls. No PINS, no monthly charges etc. I dial into a NYC number (there is also an 800# for 15 cents a call) and the service recognizes my phone and then presents me with a second dial tone and I dial the number and it connects. I have absolutely no affiliation with them, it just has proved very cost effective since I signed up arounf Christmas and I have been very happy.
http://www.gorillamobile.com/
Joe