| CallFire, Inc. | - | Santa Monica, CA | Active |
| Cambrian Communications, LLC | - | Fairfax, VA | Inactive |
| Cambridge TeleCom Services, Inc. | - | Geneseo, IL | Active |
| Camden Corporate Investments, LLC. | - | Chester, SC | Active |
| Canadian Numbering Administration Custodian | - | Ottawa, ON | Inactive |
| Cap Cable, LLC | USA Communications | Kearney, NE | Active |
| CapRock Telecommunications Corporation, Inc. | McLeodUSA | Cedar Rapids, IA | Inactive |
| CapeNet LLC | - | Westborough, MA | Inactive |
| Capital 4 Outsourcing, Inc. | - | Houston, TX | Active |
| Capital Communications Consultants, Inc. | - | Memphis, TN | Active |
| Capital Telephone Company, Inc. | - | Las Vegas, NV | Active |
| Carahsoft Technology Corporation | - | Reston, VA | Active |
| Caronet, Inc. | - | St. Petersburg, FL | Active |
| Carrera Communications, LP | - | San Antonio, TX | Active |
| Carson Communications, L.L.C. | RTC Communications, Inc. | Everest, KS | Active |
| Cass Cable TV, Inc. | - | Virginia, IL | Active |
| Castle Cable TV, Inc | - | Hammond, NY | Active |
| Cavalier Telephone, LLC | Cavalier Business Communications | Little Rock, AR | Active |
| Cbeyond Communications, LLC | - | New York, NY | Active |
| Cebridge Telecom CA, LLC. | - | St Louis, MO | Inactive |
| Cebridge Telecom LA, LLC. | - | St Louis, MO | Inactive |
| Cebridge Telecom MO, LLC. | - | St Louis, MO | Inactive |
| Cebridge Telecom NC, LLC. | Suddenlink Communications | St. Louis, MO | Inactive |
| Cebridge Telecom OK, LLC. | - | St Louis, MO | Inactive |
| Cebridge Telecom TX, LP | Cox Communications | St. Louis, MO | Inactive |
| Cebridge Telecom WV, LLC | - | St. Louis, MO | Inactive |
| Cedar Communications, LLC | - | Clarence, IA | Active |
| Cedar Communications, LLC | - | Kirkland, WA | Inactive |
| Cedar Valley Communications, Inc. | Cedar Valley Communications Inc. | Athens, TX | Inactive |
| Cedar Valley Telecommunications, Inc. | - | Cedar Falls, IA | Inactive |
| Cellular Services, LLC | - | Staffordsville, KY | Active |
| Cento Solutions Inc. | - | Upper Montclair, NJ | Inactive |
| Central Cellular LLC | COTC Connections | Davenport, OK | Active |
| Central Communications USA Inc | - | Monsey, NY | Inactive |
| Central Indiana Communications, Inc. | - | Greenfield, IN | Active |
| Central Iowa Broadband, Inc. | - | Colo, IA | Active |
| Central Nevada Communications and Electric, LLC | - | Tonopah, NV | Inactive |
| Central Valley Cable TV LLC | Central Valley Cable TV | Clovis, CA | Inactive |
| Central Wisconsin Communications, LLC | Solarus Long Distance | WISCONSIN RAPIDS, WI | Active |
| Century Tel Acquisition, LLC. | - | Monroe, LA | Inactive |
| CenturyTel Solutions, LLC | - | Monroe, LA | Inactive |
| Cequel Communications, LLC. | Suddenlink Communications | St Louis, MO | Active |
| Cequel III Communications II, LLC. | - | St Louis, MO | Inactive |
| Champion Broadband California, LLC | - | Colorado Springs, CO | Inactive |
| Champlain Broadband LLC | Burlington Telecom | Burlington, VT | Active |
| Chariton Valley Communications Corporation | - | Macon, MO | Active |
| Charter Fiberlink - Missouri, LLC | Charter Telephone Service | St Louis, MO | Active |
| Charter Fiberlink - Nebraska, LLC | Long Distance USA | St Louis, MO | Active |
| Charter Fiberlink - Pennsylvania | - | St. Louis, MO | Active |
| Charter Fiberlink AL-CCVII, LLC | - | St. Louis, MO | Active |