There are no flat rate plans available for South America offered by Cingular.

You may want to contact Cingular's customer services department for assistance in adding a feature for $3.99 that will provide you with the lowest international long distance available while traveling abroad.

Just remember that international roaming charges could be as low as .99 per minute depending country you might be going to which is one of the benefits ATTws subscribers lose once migrating to a Cingular plan.