ILLINOIS BELL TEL CO
334 prefixes in 312 · initial assignments from the NANPA CO code file, 09/17/2026
| NPA-NXX | Rate center | OCN | Assigned | Pooled |
|---|---|---|---|---|
| 312-923 | CHICGOZN01 | 9329 | — | — |
| 312-926 | CHICGOZN01 | 9329 | — | — |
| 312-928 | CHICGOZN01 | 9329 | — | Yes |
| 312-930 | CHICGOZN01 | 9329 | — | — |
| 312-931 | CHICGOZN01 | 9329 | — | Yes |
| 312-932 | CHICGOZN01 | 9329 | — | Yes |
| 312-935 | CHICGOZN01 | 9329 | — | — |
| 312-936 | CHICGOZN01 | 9329 | — | — |
| 312-938 | CHICGOZN01 | 9329 | — | — |
| 312-939 | CHICGOZN01 | 9329 | — | — |
| 312-942 | CHICGOZN01 | 9329 | — | — |
| 312-943 | CHICGOZN01 | 9329 | — | — |
| 312-944 | CHICGOZN01 | 9329 | — | — |
| 312-945 | CHICGOZN01 | 9329 | — | Yes |
| 312-946 | CHICGOZN01 | 9329 | — | — |
| 312-947 | CHICGOZN01 | 9329 | 2010-11-18 | Yes |
| 312-949 | CHICGOZN01 | 9329 | — | — |
| 312-951 | CHICGOZN01 | 9329 | — | Yes |
| 312-954 | CHICGOZN01 | 9329 | — | — |
| 312-957 | CHICGOZN01 | 9329 | — | Yes |
| 312-960 | CHICGOZN01 | 9329 | — | Yes |
| 312-970 | CHICGOZN01 | 9329 | — | Yes |
| 312-974 | CHICGOZN01 | 9329 | — | — |
| 312-977 | CHICGOZN01 | 9329 | — | — |
| 312-979 | CHICGOZN01 | 9329 | — | — |
| 312-983 | CHICGOZN01 | 9329 | — | Yes |
| 312-984 | CHICGOZN01 | 9329 | — | — |
| 312-986 | CHICGOZN01 | 9329 | — | — |
| 312-987 | CHICGOZN01 | 9329 | — | — |
| 312-988 | CHICGOZN01 | 9329 | — | Yes |
| 312-992 | CHICGOZN01 | 9329 | — | — |
| 312-993 | CHICGOZN01 | 9329 | — | Yes |
| 312-996 | CHICGOZN01 | 9329 | — | — |
| 312-997 | CHICGOZN01 | 9329 | — | Yes |
These are initial assignees from NANPA CO-code records — because of number portability, the current serving carrier of individual numbers may differ. Bulk export requires a membership.