Below is a list of all of the cell phone companies that are compatible with ChatToText.  This is current as of 17 April 09.

3 River Wireless
Advantage Communications
Airtouch Pagers
Alltel
Alltel PCS
AlphNow
Ameritech Clearpath
Ameritech Paging
Arch Pagers (PageNet)

AT&T
AT&T PCS
AT&T Pocketnet PCS
Beepwear
Bell Atlantic
Bell Canada
Bell South

Bell South (Blackberry)
Carolina Mobile Communications
Cellcom
Cellular One
Cellular One East Coast
Cellular One PCS
Cellular One South West
Cellular South (Telepak)
Central Vermont Communications

Cingular
Cingular Wireless
Clearnet
Comcast
Communication Specialist Companies
Cook Paging
Cricket
Digi-Page / Page Kansas
Fido

GrayLink / Porta-Phone
GTE
Houston Cellular
Infopage Systems
JSM Tele-Page
Koodo Mobile
Lauttamus Communication
MCI
MCI Phone

Metrocall
Metrocall 2-way
MetroPCS
Mobilecomm
Morris Wireless
Motient
Nextel
Nextel (messaging)
Nextel (page)

Ntelos
Omnipoint
OnlineBeep
Pacific Bell
PageMart
PageMart Advanced /2way
PageMart Canada
PageNet Canada
PageOne NorthWest

Primeco
ProPage
Qwest
RAM Page
Rogers Canada
Satellink
SBC Ameritech Paging
SKT Wireless
Skytel Pagers

Southern Kansas Telephone
Southern LINC
Southwestern Bell
Sprint Paging
Sprint PCS
ST Paging
SunCom
Surewest Communications
T-Mobile

Teletouch
Telus
TSR Wireless
US Cellular
US West
Verizon

Verizon Pagers
Verizon PCS
Virgin Mobile Canada
Virgin Mobile US
VoiceStream / T-Mobile
WebLink Wiereless
Wyndtell