Calling my bank in the USA because of an incorrect withdrawal is a nightmare I never want to deal with on a trip. Still, if an emergency arises or if a credit card is stolen and I must dial a toll-free USA number, I do not want to compound my misery by paying a fortune to make a phone call.
Luckily, there is a convenient service provided by AT&T that makes toll-free USA numbers accessible and free.
Before leaving home, use this AT&T site which provides dialing instructions to reach toll-free stateside numbers from 150 countries. Make note of the number(s) you will need for all the countries on your itinerary. Use the Detailed Dialing Instructions and the Dialing Demo to find out how to make the call.
Note that in some countries, only partial numbers are provided. For example, the number given for France is 0-XXX-XX-0011. If you click on the Run Dialing Demo, however, you are given the whole number which is 0-800-99-0011.
Be aware that this service is free only if you're trying to reach a toll-free number. Phone charges apply if you're dialing any other Stateside phones.
The site also supplies other useful information about phoning internationally.