Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
  • Effective date searches are available only for US area codes. Our sources for non-US NPA-NXX data do not provide this information.
  • If you want to search an entire area code regardless of activity, leave both the next and past days fields set to zero.

NPA: 406 [Rate centres in NPA 406] [Dial plan for NPA 406]

NXX: 400

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
406-400 A Havre MT HAVRMTXCDS1  958H TRIANGLE COMMUNICATION SYSTEM, INC. - MT- 648      
406-400 0 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 1 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 2 Havre MT HAVRMTXCDS1  958H TRIANGLE COMMUNICATION SYSTEM, INC. - MT- 648   2017-06-18   
406-400 3 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 4 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 5 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 6 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 7 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 8 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-07-31   
406-400 9 Havre MT GRFLMTMA7MD  453F ONVOY, LLC - MT 648   2017-09-18   

Last updated: Sat, 05 Apr 2025 03:03:23 UTC

Sponsored by: ISP Telecom

Like this site? We accept donations via PayPal.