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Area codes 678 and 470 are North American Numbering Plan area codes assigned to metropolitan Atlanta, Georgia. Both area codes are overlay codes for the numbering plan areas 404 (Atlanta) and 770 (Atlanta suburbs and exurbs). Both area codes were introduced to relieve telephone exchanges in what is one of the largest toll-free calling areas in the world. No long-distance charges are applied for calls from one portion of the area to another, regardless of the area codes.
Numbers in area code 678 were first assigned to customers signing up for new telephone service on January 15, 1998; 470 was activated on February 26, 2010. Although ten-digit dialing had been used in the Atlanta area since area code 770 was introduced in 1995, it was not until January 1, 1998, when 678 was implemented, that ten-digit dialing finally became required across the entire metro area.
All prefixes within 404 are assigned to providers, the last having been assigned in October 2013. 678 and 770 prefixes have also all been assigned to providers, leaving only 470 prefixes available, although previously-used numbers from all area codes are always available for reassignment to new customers. Despite existing for decades before this change, the largest customer using 470 is Kennesaw State University in Kennesaw, which was forced to change hundreds of telephone numbers when the Georgia Board of Regents forced schools in the University System of Georgia to implemented internal phone systems, and the FCC failed to make local number portability applicable to businesses and government, allowing AT&T to refuse KSU to take its numbers to the new provider. Kennesaw State University opted to use 470-578(KSU) as their number prefix for the new phone numbers, interestingly, outside of the normal geographical calling area for Kennesaw; 470-578 numbers are based in Atlanta Northeast and Kennesaw State University is located in the Atlanta Northwest calling area.
Area codes 678 and 470 Wikipedia
Area codes 678 and 470 serve the counties of Barrow, Bartow, Butts, Carroll, Cherokee, Clayton, Cobb, Coweta, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnett, Hall, Haralson, Heard (part with area codes 706 and 762), Henry, Lamar, Meriwether (part with area codes 706 and 762), Newton, Oconee, Paulding, Pike, Polk, Rockdale, Spalding, and Walton.