Prefix 312-227 — Chicago Zone 01, IL

NANPA CO code assignment, current as of July 28, 2026.

A phone number starting 312-227 was issued in the Chicago Zone 01 rate center of IL — part of area code 312.

NANPA's central-office code records list ILLINOIS BELL TEL CO (OCN 9329) as the code holder, assigned September 15, 2010. Because 312-227 participates in thousands-block pooling, individual 1,000-number blocks may belong to other carriers than the code holder.

A scammer can display 312-227 without ever touching IL. When in doubt, end the call and reach the company or agency through its official website; unwanted robocalls belong in the FTC's fraud report queue.

Chicago Zone 01 is part of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area. For routing purposes it sits in LATA 358. Numbers here keep Central time.

Neighboring prefixes

FAQ

Where is 312-227 located?

The prefix is assigned to the Chicago Zone 01 rate center in IL, area code 312. It is part of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area.

Which company owns 312-227 numbers?

ILLINOIS BELL TEL CO holds the code, but the prefix is pooled — individual thousands-blocks can be assigned to other carriers, and numbers may be ported to any provider.

Is a call from 312-227 safe to answer?

The prefix itself says nothing about the caller. Legitimate Chicago Zone 01 businesses and spoofed robocalls can both display it. Never share personal data with an unverified inbound caller.