Phone numbers in Castroville, California
Castroville has 6 phone prefixes in area code 831.
Biggest holders: Level 3 (Lumen), AT&T (local phone), AT&T Enterprises. This is the local calling area (rate center) where those prefixes were first assigned.
- Local phone company 33%
- Internet / business phone carrier 50%
- Phone company 17%
Every prefix in Castroville
Search the first six digits of a number in this list. If it's here, the number started in Castroville with the carrier shown. If it isn't, check the California page or look the number up.
| Prefix | Carrier | Type | Assigned |
|---|---|---|---|
| 831-307 | Level 3 (Lumen) | Internet / business phone carrier | – |
| 831-453 | AT&T Enterprises | Phone company | 2011 |
| 831-632 | AT&T (local phone) | Local phone company | – |
| 831-633 | AT&T (local phone) | Local phone company | – |
| 831-731 | IP Horizon | Internet / business phone carrier | – |
| 831-741 | Level 3 (Lumen) | Internet / business phone carrier | – |
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.