NumberResearchThousands-blocks in 858-312
This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/19/2026
The ten 1,000-number thousand-blocks inside prefix 858-312 and who was initially assigned each. Under pooling these blocks often belong to different carriers — the single prefix-level “assignee” is usually just the pool / code holder, not who holds the numbers. ← all 858 blocks
Most active assignees, all time — NPA 858
New assignments by month
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2015-06-30 | 858-312-0XXX | 0000–0999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC | 6010 | RNCHOBRNDO | CA |
| — | 858-312-1XXX | 1000–1999 | Reserved | COMCAST PHONE OF CALIFORNIA, LLC | 394L | RNCHOBRNDO | CA |
| 2004-10-19 | 858-312-2XXX | 2000–2999 | Assigned | PAETEC ITEL, LLC | 829J | RNCHOBRNDO | CA |
| 2004-10-19 | 858-312-3XXX | 3000–3999 | Assigned | PAETEC ITEL, LLC | 829J | RNCHOBRNDO | CA |
| 2004-10-19 | 858-312-4XXX | 4000–4999 | Assigned | PAETEC ITEL, LLC | 829J | RNCHOBRNDO | CA |
| 2006-01-03 | 858-312-5XXX | 5000–5999 | Assigned | COMCAST PHONE OF CALIFORNIA, LLC | 394L | RNCHOBRNDO | CA |
| 2004-01-13 | 858-312-6XXX | 6000–6999 | Assigned | COMCAST PHONE OF CALIFORNIA, LLC | 394L | RNCHOBRNDO | CA |
| 2007-03-20 | 858-312-7XXX | 7000–7999 | Assigned | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - CA | 7240 | RNCHOBRNDO | CA |
| 2008-02-22 | 858-312-8XXX | 8000–8999 | Assigned | COMCAST PHONE OF CALIFORNIA, LLC | 394L | RNCHOBRNDO | CA |
| 2016-03-14 | 858-312-9XXX | 9000–9999 | Assigned | NEW CINGULAR WIRELESS PCS, LLC | 6010 | RNCHOBRNDO | CA |
Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/19/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.