Prefix 312-678 — Chicago Zone 01, IL
- Area code
- 312
- Prefix (NXX)
- 678
- Rate center
- Chicago Zone 01
- State
- Illinois
- Time zone
- Central
- Code holder
- T-MOBILE USA, INC.
- OCN
- 6529
- Pooled
- Yes (thousands-block pooling)
- Assigned
- 2013-07-25
- LATA
- 358
The 312-678 prefix belongs to area code 312 and is anchored to the Chicago Zone 01 rate center (IL). In NANP terms, the prefix — or NXX — determines the rate center a number is billed against.
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.
The assigned code holder is T-MOBILE USA, INC., operating company number 6529, assigned July 25, 2013. This is a pooled prefix — expect numbers within it to be split across more than one carrier in 1,000-number blocks.
Caller ID showing 312-678 is not proof the call came from Chicago Zone 01: spoofing and porting both detach numbers from their origin. To verify a caller, hang up and dial the organization's published number, and report suspicious calls to the FTC.
Neighboring prefixes
| Prefix | Rate center | Code holder |
|---|---|---|
| 312-675 | Chicago Zone 01 | ILLINOIS BELL TEL CO |
| 312-676 | Chicago Zone 01 | FIRST COMMUNICATIONS, LLC |
| 312-677 | Chicago Zone 01 | SPOK, INC. |
| 312-679 | Chicago Zone 01 | U.S. TELEPACIFIC CORP. DBA TPX COMMUNICATIONS |
| 312-680 | Chicago Zone 01 | ONVOY, LLC |
| 312-681 | Chicago Zone 01 | ILLINOIS BELL TEL CO |
FAQ
Where is 312-678 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 312-678 numbers?
T-MOBILE USA, INC. 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 312-678 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.