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

HART prefixes in area code 231

NANPA records 7 assigned NXX blocks to rate center HART in area code 231, 1.2% of the 572 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. 7 holders hold those blocks, the largest being CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI (1), TWILIO INTERNATIONAL, INC. (1), 123.NET, LLC (1). The earliest assignment on record here is 2001-05-18 and the most recent 2002-08-27. 5 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 806 – overlay codes cover the same geography, so a rate center is served by all of them.

7 assigned blocks – 1.2% of 231
7 holders of record
5 of them pooled in 1,000-number lots

Prefixes assigned here

PrefixHolder of recordAssignedPooledIn service
231-301 Verizon CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI – yes yes
231-594 Twilio TWILIO INTERNATIONAL, INC. – yes yes
231-721 123.NET, LLC 2002-08-27 yes yes
231-742 AT&T NEW CINGULAR WIRELESS PCS, LLC - IL – yes yes
231-873 Frontier FRONTIER NORTH, INC. - MI – no yes
231-902 INTERACTIVE SERVICES NETWORK, INC. 2001-08-27 no yes
231-923 T-Mobile OMNIPOINT COMMUNICATIONS MIDWEST OPERATIONS, LLC 2001-05-18 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
CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI Verizon 1 14.3%
TWILIO INTERNATIONAL, INC. Twilio 1 14.3%
123.NET, LLC – 1 14.3%
NEW CINGULAR WIRELESS PCS, LLC - IL AT&T 1 14.3%
FRONTIER NORTH, INC. - MI Frontier 1 14.3%
INTERACTIVE SERVICES NETWORK, INC. – 1 14.3%
OMNIPOINT COMMUNICATIONS MIDWEST OPERATIONS, LLC T-Mobile 1 14.3%

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 HART in area code 231?

7 blocks: 301, 594, 721, 742, 873, 902, 923. The table above gives the holder of each.

Which carriers have numbers in HART?

CELLCO PARTNERSHIP DBA VERIZON WIRELESS - MI (1 block), TWILIO INTERNATIONAL, INC. (1 block), 123.NET, LLC (1 block), NEW CINGULAR WIRELESS PCS, LLC - IL (1 block), FRONTIER NORTH, INC. - MI (1 block), INTERACTIVE SERVICES NETWORK, INC. (1 block). These are the holders on record; the carrier actually serving a given number can differ, because numbers move with their owners.

Is HART 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 231

All 572 prefixes in 231