NumberResearchThousands-blocks in 928-310
This prefix’s ten 1,000-number blocks and who holds each — 10 on record · from the daily NANPA thousands-block report, 09/20/2026
The ten 1,000-number thousand-blocks inside prefix 928-310 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 928 blocks
Most active assignees, all time — NPA 928
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 928-310-0XXX | 0000–0999 | Reserved | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
| — | 928-310-1XXX | 1000–1999 | Reserved | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
| — | 928-310-2XXX | 2000–2999 | Reserved | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
| 2007-01-24 | 928-310-3XXX | 3000–3999 | Assigned | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
| 2006-08-15 | 928-310-4XXX | 4000–4999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - AZ | 6572 | FLAGSTAFF | AZ |
| 2018-05-24 | 928-310-5XXX | 5000–5999 | Assigned | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
| 2006-01-13 | 928-310-6XXX | 6000–6999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - AZ | 6572 | FLAGSTAFF | AZ |
| 2009-04-13 | 928-310-7XXX | 7000–7999 | Assigned | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
| 2005-08-17 | 928-310-8XXX | 8000–8999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - AZ | 6572 | FLAGSTAFF | AZ |
| — | 928-310-9XXX | 9000–9999 | Reserved | T-MOBILE USA, INC. | 6529 | FLAGSTAFF | AZ |
Source: NANPA Thousands Block Assignment Report (All Regions, Public), file date 09/20/2026 — Tier A primary source, refreshed on every import. Viewing is free; bulk downloads require a membership.