To find out which telephone prefixes are toll-free, visit FCC.gov. The Federal Communications Commission lists on its website the six three-digit toll-free prefixes as of 2015 and explains how they are assigned.
On the homepage, click the Guides tab, and then click More to access the Consumer Publications Library. Scroll down to the Telephone: Bills and Charges header and click on the What Is a Toll-Free Number and How Does It Work? link.
The FCC explains that 800, 888, 877, 866, 855 and 844 are the six unique toll-free three-digit prefixes in use in the United States. They are not interchangeable; the prefixes are assigned on a first-come, first-served basis. Calls to toll-free numbers are routed to another local telephone number.
844 is the newest toll-free prefix as of 2015, in use since December 7, 2013. Prefixes reserved for future expansion include 833, 822, 880 through 887 and 889.
Toll-free numbers have proven to be successful business tools, according to the FCC, especially in customer service and telemarketing. The charge for using a toll-free number is paid by the called party instead of the calling party, meaning customers have a free way to contact businesses.
To file complaint against a company providing toll-free numbers on the FCC's website.