| Coin Telecom, Inc. | Coin Telecom | St John, WA | Inactive |
| Coleman County Telecommunications, Ltd. | - | Santa Anna, TX | Inactive |
| Coleman Enterprises, Inc. | Local Long Distance | Kalamazoo, MI | Inactive |
| Collateral Network Solutions, LLC | - | Tulsa, OK | Active |
| Colorado River Communication | - | Las Vegas, NV | Inactive |
| Colorado Valley Communications, Inc. | Colorado Valley Long Distance, Inc. | La Grange, TX | Active |
| ComLinq, Inc. | - | ALEDO, TX | Inactive |
| ComSouth Teleservices, Inc. | - | Hawkinsville, GA | Inactive |
| ComTech21, LLC | - | Wallingford, CT | Active |
| Comanche County Telecommunications, Inc. | Comanche County Long Distance | De Leon, TX | Active |
| Combined Billing Corporation | - | Daytona Beach, FL | Active |
| Comdata Telecommunications Services, Inc. | - | Brentwood, TN | Inactive |
| Comity Communications, LLC | - | Des Moines, IA | Active |
| Comm South Companies, Inc. | - | Dallas, TX | Inactive |
| Comm/Net Services Corporation | - | Plano, TX | Inactive |
| Commas Communications Inc | - | Brooklyn, NY | Inactive |
| CommuniGroup of K.C., Inc. (CGI) | CGI Long Distance Services | Mission, KS | Inactive |
| CommuniGroup of Louisiana, Inc. | - | Monroe, LA | Inactive |
| Communicate Technological Systems, LLC | - | Houston, TX | Inactive |
| Communication Data and Security, Inc. | Communication Data and Secuirty, Inc. | Spring Valley, NY | Inactive |
| Communication Services Integrated Inc. CSII | COMMUNICATION SERVICES INTEGRATED, INC. | Carrollton, GA | Active |
| Communication Technology, Inc. | - | Hollywood, FL | Inactive |
| Communication Telefonicas Latinas Corp. | - | Alpharetta, GA | Active |
| Communications Design Acquisition LLC | Pine Tree Networks | New Gloucester, ME | Inactive |
| Communications Design, Inc. | - | Alexandria, MN | Inactive |
| Communications Distributors, Inc. | - | Kingwood, TX | Inactive |
| Communications Network Billing, Inc. | - | Harper Woods, MI | Active |
| Communications Network Services, LLC | - | Greenwood Village, CO | Inactive |
| Communications Pioneer | - | Brooklyn, NY | Active |
| Communications Support Services, Inc. | - | Miami, FL | Inactive |
| Community Long Distance | Comporium Long Distance | Rock Hill, SC | Active |
| Comoretel Holdings Ltd. | - | Omaha, NE | Active |
| Compass Telecommunications, Inc. | - | Scottsdale, AZ | Active |
| Complete Communication Services | - | Stratford, IA | Active |
| Computer Integrated Services, LLC | - | New York, NY | Inactive |
| Computer Technology Solutions, Inc. | Integrated Technology Services | Miami Gardens, FL | Active |
| ComputerTel, Inc. | - | Carson City, NV | Active |
| Comtech, LLC | Comtech | Reston, VA | Inactive |
| Comteck of Indiana, Inc. | - | Sweetser, IN | Active |
| Comtel Computer Corp. | COMTEL Computer Corp. | Westminster, CO | Inactive |
| Conectado, Inc. | - | Henderson, NV | Active |
| Connect America, Inc | - | Naperville, IL | Inactive |
| Connecting International Busines, Inc. | - | Miami, FL | Inactive |
| Consolidated Billing Provider, LLC | Direct Access Group LLC | Casselberry, FL | Inactive |
| Consolidated Communications of Comerco Company | Consolidated Communications | Mattoon, IL | Active |
| Consolidated Long Distance, Inc. | - | Lincoln, NE | Active |
| Consumer Telcom, Inc. | Consumer Telcom, inc. | Henderson Valley, NV | Inactive |
| Continental Long Distance Corporation | Continental Long Distance | Spring Branch, TX | Active |
| Continental Systems and Technologies, Inc. | - | Hicksville, NY | Inactive |
| Continental Telecommunications Services, Inc. | CTS | Boston, MA | Inactive |