Phone numbers in Guilford, Connecticut
Guilford has 11 phone prefixes in area codes 203, 475.
Biggest holders: AT&T (local phone), Onvoy, Teleport Communications America. This is the local calling area (rate center) where those prefixes were first assigned.
- Local phone company 36%
- Internet / business phone carrier 64%
Every prefix in Guilford
Search the first six digits of a number in this list. If it's here, the number started in Guilford with the carrier shown. If it isn't, check the Connecticut page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 203-204 | Teleport Communications America | Internet / business phone carrier | – |
| 203-453 | AT&T (local phone) | Local phone company | – |
| 203-457 | AT&T (local phone) | Local phone company | – |
| 203-458 | AT&T (local phone) | Local phone company | – |
| 203-533 | Level 3 (Lumen) | Internet / business phone carrier | – |
| 203-689 | AT&T (local phone) | Local phone company | – |
| 203-738 | Windstream (PAETEC) | Internet / business phone carrier | – |
| 203-884 | Onvoy | Internet / business phone carrier | – |
| 475-274 | Bandwidth | Internet / business phone carrier | 2020 |
| 475-401 | Onvoy | Internet / business phone carrier | 2026 |
| 475-900 | Onvoy | Internet / business phone carrier | 2019 |
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.