NumberingData
Verified Nov 1, 2026 · Source: NANPA CO Code Assignment Records

CASTROVL prefixes in area code 830

NANPA records 6 assigned NXX blocks to rate center CASTROVL in area code 830, 1.2% of the 496 blocks assigned in the code. A rate center is the billing geography a block is allocated to – NANPA truncates the name to ten characters, so read it as a NANPA label rather than a town. 5 holders hold those blocks, the largest being SOUTHWESTERN BELL (2), TELNYX LLC (1), TELEPORT COMMUNICATIONS AMERICA, LLC - TX (1). The earliest assignment on record here is 2017-03-15 and the most recent 2021-10-25. 6 of them are in thousands-block pooling, so those prefixes are shared between carriers in 1,000-number lots. The same rate center name also appears in area code 831 – overlay codes cover the same geography, so a rate center is served by all of them.

6 assigned blocks – 1.2% of 830
5 holders of record
6 of them pooled in 1,000-number lots

Prefixes assigned here

PrefixHolder of recordAssignedPooledIn service
830-346 Telnyx TELNYX LLC 2017-03-15 yes yes
830-349 AT&T TELEPORT COMMUNICATIONS AMERICA, LLC - TX 2021-10-25 yes yes
830-355 Lumen LEVEL 3 COMMUNICATIONS, LLC - TX – yes yes
830-521 MATRIX TELECOM, LLC. S/I/I TNCI - TX – yes yes
830-538 AT&T SOUTHWESTERN BELL – yes yes
830-931 AT&T SOUTHWESTERN BELL – yes yes

The holder is who received the block from the numbering administrator. It is not necessarily the carrier serving a given number: numbers move with their owners, and a pooled block is shared.

Who holds the blocks

HolderBrandBlocksShare here
SOUTHWESTERN BELL AT&T 2 33.3%
TELNYX LLC Telnyx 1 16.7%
TELEPORT COMMUNICATIONS AMERICA, LLC - TX AT&T 1 16.7%
LEVEL 3 COMMUNICATIONS, LLC - TX Lumen 1 16.7%
MATRIX TELECOM, LLC. S/I/I TNCI - TX – 1 16.7%

Same rate center in other codes

Overlay codes cover the same geography, so one rate center is served by all of them.

Frequently asked

Which prefixes belong to CASTROVL in area code 830?

6 blocks: 346, 349, 355, 521, 538, 931. The table above gives the holder of each.

Which carriers have numbers in CASTROVL?

SOUTHWESTERN BELL (2 blocks), TELNYX LLC (1 block), TELEPORT COMMUNICATIONS AMERICA, LLC - TX (1 block), LEVEL 3 COMMUNICATIONS, LLC - TX (1 block), MATRIX TELECOM, LLC. S/I/I TNCI - TX (1 block). These are the holders on record; the carrier actually serving a given number can differ, because numbers move with their owners.

Is CASTROVL a city?

It is a rate center – the unit NANPA allocates number blocks to. Its name is abbreviated to ten characters and is not necessarily a settlement: we print it as recorded rather than guess at the full name.

Other rate centers in 830

All 496 prefixes in 830