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

WINTHROP prefixes in area code 857

NANPA records 6 assigned NXX blocks to rate center WINTHROP in area code 857, 1.7% of the 361 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 ONVOY, LLC - MA (2), METROPCS, INC. (1), BANDWIDTH.COM CLEC, LLC - MA (1). The earliest assignment on record here is 2001-03-20 and the most recent 2024-11-07. 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 codes 207, 315, 319, 507 – overlay codes cover the same geography, so a rate center is served by all of them.

6 assigned blocks – 1.7% of 857
5 holders of record
6 of them pooled in 1,000-number lots

Prefixes assigned here

PrefixHolder of recordAssignedPooledIn service
857-201 T-Mobile METROPCS, INC. 2002-10-28 yes yes
857-336 Onvoy ONVOY, LLC - MA 2016-03-01 yes yes
857-349 Bandwidth BANDWIDTH.COM CLEC, LLC - MA 2018-09-20 yes yes
857-597 Onvoy ONVOY, LLC - MA 2021-04-01 yes yes
857-816 Verizon MCIMETRO ACCESS TRANSMISSION SERVICES LLC 2001-03-20 yes yes
857-833 Charter ONVOY SPECTRUM, LLC 2024-11-07 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
ONVOY, LLC - MA Onvoy 2 33.3%
METROPCS, INC. T-Mobile 1 16.7%
BANDWIDTH.COM CLEC, LLC - MA Bandwidth 1 16.7%
MCIMETRO ACCESS TRANSMISSION SERVICES LLC Verizon 1 16.7%
ONVOY SPECTRUM, LLC Charter 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 WINTHROP in area code 857?

6 blocks: 201, 336, 349, 597, 816, 833. The table above gives the holder of each.

Which carriers have numbers in WINTHROP?

ONVOY, LLC - MA (2 blocks), METROPCS, INC. (1 block), BANDWIDTH.COM CLEC, LLC - MA (1 block), MCIMETRO ACCESS TRANSMISSION SERVICES LLC (1 block), ONVOY SPECTRUM, LLC (1 block). These are the holders on record; the carrier actually serving a given number can differ, because numbers move with their owners.

Is WINTHROP 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 857

All 361 prefixes in 857