Only 1 more thing to add to one of the other posters. Just be careful when calling supposed freephone numbers from a mobile. My provider "Orange" appear to have a department that thrives on locating each and every calling card or cheap telecom provider here in the UK. After I enter the 0800 number I invariably get a message warning me that it is a local call rate plus of course whatever the other telco is going to charge! So much for the spirit of free competition!!
Not sure if they will be that smart in the US but worth digging around before chatting on the phone for hours and finding out later that they were charging your normal call rates all along.