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 |
|---|---|---|---|---|
| 312-201 | CHICGOZN01 | 9329 | — | — |
| 312-202 | CHICGOZN01 | 9329 | — | Yes |
| 312-204 | CHICGOZN01 | 9329 | — | Yes |
| 312-207 | CHICGOZN01 | 9329 | — | Yes |
| 312-212 | CHICGOZN01 | 9329 | — | Yes |
| 312-214 | CHICGOZN01 | 9329 | — | — |
| 312-220 | CHICGOZN01 | 9329 | — | — |
| 312-222 | CHICGOZN01 | 9329 | — | — |
| 312-223 | CHICGOZN01 | 9329 | — | — |
| 312-225 | CHICGOZN01 | 9329 | — | — |
| 312-226 | CHICGOZN01 | 9329 | — | — |
| 312-227 | CHICGOZN01 | 9329 | 2010-09-15 | Yes |
| 312-228 | CHICGOZN01 | 9329 | — | — |
| 312-229 | CHICGOZN01 | 9329 | — | Yes |
| 312-230 | CHICGOZN01 | 9329 | — | Yes |
| 312-233 | CHICGOZN01 | 9329 | — | Yes |
| 312-234 | CHICGOZN01 | 9329 | — | Yes |
| 312-235 | CHICGOZN01 | 9329 | — | Yes |
| 312-236 | CHICGOZN01 | 9329 | — | — |
| 312-240 | CHICGOZN01 | 9329 | — | — |
| 312-243 | CHICGOZN01 | 9329 | — | — |
| 312-244 | CHICGOZN01 | 9329 | — | Yes |
| 312-245 | CHICGOZN01 | 9329 | — | — |
| 312-251 | CHICGOZN01 | 9329 | — | — |
| 312-255 | CHICGOZN01 | 9329 | — | Yes |
| 312-258 | CHICGOZN01 | 9329 | — | — |
| 312-263 | CHICGOZN01 | 9329 | — | — |
| 312-266 | CHICGOZN01 | 9329 | — | — |
| 312-267 | CHICGOZN01 | 9329 | — | Yes |
| 312-269 | CHICGOZN01 | 9329 | — | — |
| 312-274 | CHICGOZN01 | 9329 | — | — |
| 312-280 | CHICGOZN01 | 9329 | — | — |
| 312-291 | CHICGOZN01 | 9329 | — | Yes |
| 312-293 | CHICGOZN01 | 9329 | — | — |
| 312-294 | CHICGOZN01 | 9329 | — | — |
| 312-297 | CHICGOZN01 | 9329 | — | — |
| 312-302 | CHICGOZN01 | 9329 | — | — |
| 312-306 | CHICGOZN01 | 9329 | — | — |
| 312-308 | CHICGOZN01 | 9329 | — | — |
| 312-309 | CHICGOZN01 | 9329 | — | — |
| 312-321 | CHICGOZN01 | 9329 | — | — |
| 312-322 | CHICGOZN01 | 9329 | — | — |
| 312-325 | CHICGOZN01 | 9329 | 2003-06-24 | Yes |
| 312-326 | CHICGOZN01 | 9329 | — | — |
| 312-328 | CHICGOZN01 | 9329 | — | — |
| 312-329 | CHICGOZN01 | 9329 | — | — |
| 312-332 | CHICGOZN01 | 9329 | — | — |
| 312-335 | CHICGOZN01 | 9329 | — | — |
| 312-336 | CHICGOZN01 | 9329 | — | — |
| 312-337 | CHICGOZN01 | 9329 | — | — |
| 312-338 | CHICGOZN01 | 9329 | — | — |
| 312-341 | CHICGOZN01 | 9329 | — | — |
| 312-344 | CHICGOZN01 | 9329 | — | Yes |
| 312-345 | CHICGOZN01 | 9329 | — | — |
| 312-346 | CHICGOZN01 | 9329 | — | — |
| 312-347 | CHICGOZN01 | 9329 | — | — |
| 312-353 | CHICGOZN01 | 9329 | — | — |
| 312-355 | CHICGOZN01 | 9329 | — | — |
| 312-356 | CHICGOZN01 | 9329 | — | — |
| 312-357 | CHICGOZN01 | 9329 | — | — |
| 312-360 | CHICGOZN01 | 9329 | — | — |
| 312-361 | CHICGOZN01 | 9329 | — | Yes |
| 312-362 | CHICGOZN01 | 9329 | — | — |
| 312-364 | CHICGOZN01 | 9329 | — | — |
| 312-368 | CHICGOZN01 | 9329 | — | — |
| 312-372 | CHICGOZN01 | 9329 | — | — |
| 312-374 | CHICGOZN01 | 9329 | — | Yes |
| 312-380 | CHICGOZN01 | 9329 | — | Yes |
| 312-381 | CHICGOZN01 | 9329 | — | Yes |
| 312-382 | CHICGOZN01 | 9329 | — | — |
| 312-384 | CHICGOZN01 | 9329 | — | Yes |
| 312-385 | CHICGOZN01 | 9329 | — | Yes |
| 312-386 | CHICGOZN01 | 9329 | — | Yes |
| 312-394 | CHICGOZN01 | 9329 | — | Yes |
| 312-396 | CHICGOZN01 | 9329 | — | — |
| 312-397 | CHICGOZN01 | 9329 | — | — |
| 312-407 | CHICGOZN01 | 9329 | — | — |
| 312-408 | CHICGOZN01 | 9329 | — | — |
| 312-409 | CHICGOZN01 | 9329 | — | Yes |
| 312-410 | CHICGOZN01 | 9329 | — | — |
| 312-413 | CHICGOZN01 | 9329 | — | — |
| 312-417 | CHICGOZN01 | 9329 | — | — |
| 312-419 | CHICGOZN01 | 9329 | — | — |
| 312-421 | CHICGOZN01 | 9329 | — | — |
| 312-422 | CHICGOZN01 | 9329 | — | — |
| 312-424 | CHICGOZN01 | 9329 | — | — |
| 312-425 | CHICGOZN01 | 9329 | — | — |
| 312-427 | CHICGOZN01 | 9329 | — | — |
| 312-430 | CHICGOZN01 | 9329 | — | — |
| 312-431 | CHICGOZN01 | 9329 | — | — |
| 312-432 | CHICGOZN01 | 9329 | — | — |
| 312-433 | CHICGOZN01 | 9329 | — | Yes |
| 312-435 | CHICGOZN01 | 9329 | — | — |
| 312-436 | CHICGOZN01 | 9329 | — | Yes |
| 312-440 | CHICGOZN01 | 9329 | — | — |
| 312-441 | CHICGOZN01 | 9329 | — | — |
| 312-442 | CHICGOZN01 | 9329 | — | Yes |
| 312-443 | CHICGOZN01 | 9329 | — | Yes |
| 312-444 | CHICGOZN01 | 9329 | — | Yes |
| 312-445 | 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.