Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
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NPA: 231 [Rate centres in NPA 231] [Dial plan for NPA 231]

NXX: 721

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
231-721 A Hart MI GDRPMIBLX8Z  2550 123.NET, LLC 348      
231-721 0 Hart MI   2550 123.NET, LLC 348      
231-721 1 Hart MI   6003 CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI 348   2021-04-20   
231-721 2 Hart MI   543C ONVOY, LLCV - MI 348   2020-11-20   
231-721 3 Hart MI   543C ONVOY, LLCV - MI 348   2020-11-20   
231-721 5 Hart MI   6003 CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI 348   2012-09-24   
231-721 6 Hart MI   624H ONVOY SPECTRUM, LLC 348   2021-06-19   
231-721 7 Hart MI   508J CENTURYLINK COMMUNICATIONS, LLC 348   2017-10-04   
231-721 9 Hart MI   2964 OMNIPOINT COMMUNICATIONS MIDWEST OPERATIONS, LLC 348   2024-01-16   

Last updated: Tue, 13 Jan 2026 21:50:02 UTC

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