Just pick up the phone and call the 800 number.

Your calling card might charge a small surcharge of maybe 50 cents to a dollar for using the 800 number.

Other than that, it's probably quite cheap. They don't have huge banks of pay phones they way they used to, but she'll be able to find one.

The only drawback is that if you spend an hour telling each other how much you love and miss each other, she'll be on her feet the whole time.