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

ROCK prefixes in area code 906

NANPA records 4 assigned NXX blocks to rate center ROCK in area code 906, 1.1% of the 360 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. 4 holders hold those blocks, the largest being INTERACTIVE SERVICES NETWORK, INC. (1), MICHIGAN BELL TEL CO (1), BARAGA TELEPHONE COMPANY (1). The earliest assignment on record here is 2001-07-30 and the most recent 2021-01-06. 2 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 620 – overlay codes cover the same geography, so a rate center is served by all of them.

4 assigned blocks – 1.1% of 906
4 holders of record
2 of them pooled in 1,000-number lots

Prefixes assigned here

PrefixHolder of recordAssignedPooledIn service
906-325 INTERACTIVE SERVICES NETWORK, INC. – no yes
906-356 AT&T MICHIGAN BELL TEL CO – yes yes
906-357 BARAGA TELEPHONE COMPANY 2001-07-30 no yes
906-444 Onvoy ONVOY, LLCV - MI 2021-01-06 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
INTERACTIVE SERVICES NETWORK, INC. – 1 25%
MICHIGAN BELL TEL CO AT&T 1 25%
BARAGA TELEPHONE COMPANY – 1 25%
ONVOY, LLCV - MI Onvoy 1 25%

Frequently asked

Which prefixes belong to ROCK in area code 906?

4 blocks: 325, 356, 357, 444. The table above gives the holder of each.

Which carriers have numbers in ROCK?

INTERACTIVE SERVICES NETWORK, INC. (1 block), MICHIGAN BELL TEL CO (1 block), BARAGA TELEPHONE COMPANY (1 block), ONVOY, LLCV - MI (1 block). These are the holders on record; the carrier actually serving a given number can differ, because numbers move with their owners.

Is ROCK 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 906

All 360 prefixes in 906