The subject behavior occurs in locales that have multiple area codes for local phone calls. In Alpharetta Georgia, which is part of metropolitan Atlanta, I can call 770, 678, 404, and 706 as local (free) phone calls.
To resolve this issue:
1. Open Control Panel and double-click Phone And Modem Options.
2. Press Dialing Rules.
3. Select the dialing location and press Edit.
4. Press Area Code Rules.
5. Press New.
6. Select Include only the prefixes in the list below and add the appropriate prefixes for your locale.
7. Press OK.