Prefix 312-620 — Chicago Zone 01, IL

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

Area code
312
Prefix (NXX)
620
Rate center
Chicago Zone 01
State
Illinois
Time zone
Central
Code holder
BANDWIDTH.COM CLEC, LLC - IL
OCN
984E
Pooled
Yes (thousands-block pooling)
Assigned
2012-08-15
LATA
358

Numbers in the 312-620 prefix are registered to the Chicago Zone 01 rate center in IL, inside area code 312. The prefix is the second block of a ten-digit US number (312-620-XXXX) and pins the number to a billing locality.

NANPA's central-office code records list BANDWIDTH.COM CLEC, LLC - IL (OCN 984E) as the code holder, assigned August 15, 2012. Because 312-620 participates in thousands-block pooling, individual 1,000-number blocks may belong to other carriers than the code holder.

The rate center lies in the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area. The serving LATA is 358. Local time follows the Central zone.

Spoofing means this prefix on your screen doesn't guarantee a Chicago Zone 01 caller. Verify independently before trusting a request for money or data.

Neighboring prefixes

Prefixes adjacent to 312-620
PrefixRate centerCode holder
312-617 Chicago Zone 01 T-MOBILE USA, INC.
312-618 Chicago Zone 01 NEW CINGULAR WIRELESS PCS, LLC - IL
312-619 Chicago Zone 01 T-MOBILE USA, INC.
312-621 Chicago Zone 01 ILLINOIS BELL TEL CO
312-622 Chicago Zone 01 NEW CINGULAR WIRELESS PCS, LLC - IL
312-623 Chicago Zone 01 NEW CINGULAR WIRELESS PCS, LLC - IL

FAQ

Where is 312-620 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 312-620 numbers?

BANDWIDTH.COM CLEC, LLC - IL 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 312-620 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.