Toll-free numbers are assigned by RespOrgs (Responsible Organizations). When getting toll-free numbers, the FCC requires the toll-free numbers to be portable, so a business can port their number to a new RespOrg if they switch providers.
Toll-free numbers are free for the caller. However, an international call to a toll-free number attracts charges. It only allows a toll free call when calling from within the same country irrespective of the distance.