Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
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NPA: 605 [Rate centres in NPA 605] [Dial plan for NPA 605]

NXX: 621

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
605-621 A Madison SD WTTWSDCO0MD  907D INTERSTATE TELECOMMUNICATIONS COOPERATIVE, INC. 640      
605-621 0 Madison SD SXFLSDCOX1X  073H TELNYX LLC 640   2023-09-30   
605-621 1 Madison SD SXFLSDPS1MD  939H COMMIO, LLC 640   2023-10-13   
605-621 2 Madison SD SXFLSDPS1MD  939H COMMIO, LLC 640   2023-10-13   
605-621 3 Madison SD SXFLSDPS1MD  939H COMMIO, LLC 640   2023-10-13   
605-621 4 Madison SD SXFLSDPS1MD  939H COMMIO, LLC 640   2023-10-13   
605-621 5 Madison SD SXFLSDPS1MD  939H COMMIO, LLC 640   2023-10-13   
605-621 6 Madison SD SXFLSDCOX0X  624H ONVOY SPECTRUM, LLC 640   2024-12-20   
605-621 7 Madison SD SXFLSDCOTMD  162G ONVOY, LLC - SD 640   2024-07-14   
605-621 9 Madison SD WTTWSDCO0MD  907D INTERSTATE TELECOMMUNICATIONS COOPERATIVE, INC. 640   2023-05-04   

Last updated: Thu, 16 Oct 2025 03:04:18 UTC

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