NumberResearchThousands-blocks in 972-521
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 972-521 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 972 blocks
Most active assignees, all time — NPA 972
New assignments by month
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| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| — | 972-521-0XXX | 0000–0999 | Reserved | LEVEL 3 OF TELECOM OF TEXAS, LLC - TX | 7516 | ALLEN | TX |
| 2012-03-27 | 972-521-1XXX | 1000–1999 | Assigned | BANDWIDTH.COM CLEC, LLC - TX | 004F | ALLEN | TX |
| 2014-03-25 | 972-521-2XXX | 2000–2999 | Assigned | FRONTIER SOUTHWEST INC DBA FRONTIER COMM OF TEXAS | 0701 | ALLEN | TX |
| 2012-09-13 | 972-521-3XXX | 3000–3999 | Assigned | ONVOY, LLC - TX | 903C | ALLEN | TX |
| 2013-11-12 | 972-521-4XXX | 4000–4999 | Assigned | ONVOY, LLC - TX | 903C | ALLEN | TX |
| — | 972-521-5XXX | 5000–5999 | Reserved | LEVEL 3 OF TELECOM OF TEXAS, LLC - TX | 7516 | ALLEN | TX |
| 2013-11-12 | 972-521-6XXX | 6000–6999 | Assigned | ONVOY, LLC - TX | 903C | ALLEN | TX |
| 2008-07-08 | 972-521-7XXX | 7000–7999 | Assigned | ONVOY, LLC - TX | 903C | ALLEN | TX |
| 2011-04-25 | 972-521-8XXX | 8000–8999 | Assigned | BANDWIDTH.COM CLEC, LLC - TX | 004F | ALLEN | TX |
| 2011-04-25 | 972-521-9XXX | 9000–9999 | Assigned | BANDWIDTH.COM CLEC, LLC - TX | 004F | ALLEN | TX |
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.