CHICGOZN04 — IL
Data last updated: March 10, 2026
Area Codes
Top Carriers
| Carrier | OCN | NXX Count |
|---|---|---|
| ILLINOIS BELL TEL CO | 9329 | 42 |
| T-MOBILE USA, INC. | 6529 | 14 |
| ONVOY, LLC | 224C | 7 |
| LEVEL 3 COMMUNICATIONS, LLC - IL | 6115 | 6 |
| MCIMETRO ACCESS TRANSMISSION SERVICES LLC | 7229 | 5 |