NumberResearchThousands-blocks in 231-375
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 231-375 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 231 blocks
Most active assignees, all time — NPA 231
New assignments by month
Sep 2026
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Oct 2025
| Assigned | Thousands-block | Last 4 digits | Status | Assignee | OCN | Rate center | State |
|---|---|---|---|---|---|---|---|
| 2015-10-21 | 231-375-0XXX | 0000–0999 | Assigned | COMCAST IP PHONE, LLC | 318J | MUSKEGON | MI |
| 2018-01-05 | 231-375-1XXX | 1000–1999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI | 6003 | MUSKEGON | MI |
| 2014-06-03 | 231-375-2XXX | 2000–2999 | Assigned | MCIMETRO ACCESS TRANSMISSION SERVICES LLC - MI | 7157 | MUSKEGON | MI |
| 2014-02-24 | 231-375-3XXX | 3000–3999 | Assigned | METROPCS, INC. | 5562 | MUSKEGON | MI |
| 2014-02-24 | 231-375-4XXX | 4000–4999 | Assigned | METROPCS, INC. | 5562 | MUSKEGON | MI |
| 2014-01-22 | 231-375-5XXX | 5000–5999 | Assigned | COMCAST IP PHONE, LLC | 318J | MUSKEGON | MI |
| 2015-06-25 | 231-375-6XXX | 6000–6999 | Assigned | CENTURYLINK COMMUNICATIONS, LLC | 508J | MUSKEGON | MI |
| 2014-08-04 | 231-375-7XXX | 7000–7999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI | 6003 | MUSKEGON | MI |
| 2015-03-17 | 231-375-8XXX | 8000–8999 | Assigned | COMCAST IP PHONE, LLC | 318J | MUSKEGON | MI |
| 2014-08-20 | 231-375-9XXX | 9000–9999 | Assigned | CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI | 6003 | MUSKEGON | MI |
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.