Local Calling Guide

Area code/prefix search

Search area code/prefix (NPA/NXX)
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NPA: 312 [Rate centres in NPA 312] [Dial plan for NPA 312]

NXX: 245

NPA-NXX BLOCK Rate Centre Region Switch OCN LATA LIR Eff date Disc date
312-245 A Chicago Zone 01-Illinois Dearborn IL CHCGILIDDS0  9329 ILLINOIS BELL TEL CO 358      

Last updated: Sun, 07 Dec 2025 22:02:11 UTC

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