Phone numbers in Seneca, Illinois
Seneca has 4 phone prefixes in area code 815.
Biggest holders: AT&T (local phone), Onvoy, Level 3 (Lumen). This is the local calling area (rate center) where those prefixes were first assigned.
- Local phone company 50%
- Internet / business phone carrier 50%
Every prefix in Seneca
Search the first six digits of a number in this list. If it's here, the number started in Seneca with the carrier shown. If it isn't, check the Illinois page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 815-357 | AT&T (local phone) | Local phone company | – |
| 815-415 | AT&T (local phone) | Local phone company | – |
| 815-755 | Onvoy | Internet / business phone carrier | 2016 |
| 815-769 | Level 3 (Lumen) | Internet / business phone carrier | 2001 |
Most prefixes are pooled: the 10,000 numbers in each are handed out in blocks of 1,000 to different carriers, and people can also take their numbers to another carrier. So the carrier shown is where the prefix started, not a guarantee about any one number. Source: NANPA central office code records, 2026-10-10.