| CoID | Company | Type | Status | States Served | 24X7 Phone |
| ATCID | ATC Communications Inc. | ILEC | A | ID | 208-673-5335 |
| ATCMD | Armstrong Telephone Company - Maryland | ILEC | A | MD | 877-277-5709 |
| ATCN | Armstrong Telephone Company - North | ILEC | A | PA | 877-277-5709 |
| ATCND | Armstrong Telephone Co Northern Div. | ILEC | A | WV | 877-277-5709 |
| ATCNE | ATC Communications | ILEC | A | NE | 308-962-7298 |
| ATCNY | Armstrong Telephone Company | ILEC | A | NY | 877-277-5709 |
| ATCO | Ardmore Telephone Company Inc. | ILEC VoIP Reseller | A | AL | TN | 270-856-1033 |
| ATCPA | Armstrong Telephone Company - PA | ILEC | A | PA | 877-277-5709 |
| ATCTC | American Telephone Company | CLEC Facility CLEC Reseller VoIP Reseller VoIP Provider | A | USA - Nation Wide | 888-943-8282 |
| ATCWV | Armstrong Telephone Company - WV | ILEC | A | WV | 877-277-5709 |
| ATEL | Adams TelSystems Inc. | CLEC Facility CLEC UNE VoIP Reseller VoIP Provider | A | IL | 217-696-4411 |
| ATG | ATG Communications LLC | VoIP Reseller VoIP Provider | A | USA - Nation Wide | 706-823-1449 opt 2 |
| ATG23 | Applied Technology Group | | A | | 260-482-2844 |
| ATGCO | ATG Corp. - CANCELLED | VoIP Reseller VoIP Provider | C | USA - Nationwide | 208-906-8320 |
| ATGI | Advanced Telecom | 9-1-1 Admin-CPE ALI (9-1-1 Jurisdiction/PSAP ONLY) | PBX | A | CA | NV | OR | WA | 877-679-9432 |
| ATHER | Atheral LLC | VoIP Reseller VoIP Provider | A | USA - Nationwide | 702-470-2766 |
| ATHR | The Arthur Mutual Telephone Co. | LEC | A | OH | 419-393-2233 |
| ATI | Affinity Telecom, Inc.(Cancelled) | CLEC Faciliy, CLEC Reseller, CLEC UNE | C | CO | 303-961-0022 |
| ATIAR | Armstrong Telecommunications Inc | CLEC Facility | A | KY | MD | NY | OH | PA | WV | 877-277-5709 |
| ATIMN | ATI (Cancelled - See ESCH) | Facility | C | MN | 612-964-5794 |
| ATLAS | Atlas Electric Devices (Cancelled) | Facility | C | IL | 773-327-4520 |
| ATLC | Atlantic Telecom Multimedia Consolidated | CLEC Facility | A | NC | 910-754-1730 |
| ATMC | Atlantic Telephone Membership Corp | Co-Op/Rural ILEC | A | NC | 910-754-1730 |
| ATN | All Tel Networks LLC | VoIP Provider | A | USA - Nationwide | 772-215-1140 |
| ATS | ATS Telecommunications (Cancelled) | Facility | C | TX | 888-326-3302 |
| ATSLC | ATS Services, LLC (Cancelled) | Reseller | C | Illinois Counties: Cook, Kane, Lake, McHenry, DuPage, Will | 888-675-6347 |
| ATTBB | Insight Phone of Kentucky, LLC (CANCELLED) | Facility | C | OH | 800-771-9124 |
| ATTCS | AT&T Consumer Services, Inc (Cancelled) | CLEC Facility | C | ALL | 888-249-4980 |
| ATTI | A-Tech Telecom, Inc. (Cancelled) | UNE | C | TX,KY,AR | 972-527-2488 |
| ATTIS | AT&T | CLEC Facility ILEC VPC | A | USA - Nationwide | 877-450-1990 |
| ATTLS | AT&T | CLEC Reseller | A | CA | NV | 800-275-0014 |
| ATTMO | AT&T Mobility | Wireless/Cellular/PCS | A | USA - Nation Wide | 800-635-6840 opt. 4 |
| ATTPS | AT&T (Cancelled) | PS ALI | C | National | 888-249-4980 |
| ATTSP | AT&T Mobility | Wireless/Cellular/PCS | A | USA - Nationwide | 800-635-6840 opt. 4 |
| ATTWS | AT&T Wireless Services, Inc. (CANCELLED-See CING) | Wireless | C | ALL States | 800-635-6840 |
| ATU | ATU Telecommunications (Out of Business) | Facility | C | Anchorage, Byrd, Indian, Girdwood, Portage, Hope, AK | 907-564-1642 |
| ATUED | Arkansas Tech University | PBX/PS911/Shared Tenant | A | AR | 479-968-0646 |
| ATZ | ATX Telecommunications Services (Cancelled) | Reseller | C | PA, NJ, DE | 610-668-3000 |
| AUBN | Knology Inc. | CLEC Facility | A | | 877-566-5649 |
| AUD | Audian Inc. | VoIP Reseller VoIP Provider | A | USA - Nation Wide | 844-611-6110 |
| AUSER | Anyuser, Inc. (CANCELLED) | VoIP | C | CA | 858-831-0500 |
| AUSW | CSC WIRELESS LLC dba. ALTICE MOBILE | Wireless/Cellular/PCS | A | USA - Nationwide | 866-232-5455 |
| AVADV | AVAD Technologies | VoIP Reseller | A | USA - Nationwide | 800-733-4165 |
| AVAYA | Avaya | VoIP Provider | A | USA - Nationwide | 866-462-8292 |
| AVDNE | Advanced VoIP Data | VoIP Provider | A | USA - Nationwide | 248-313-2300 |
| AVF | Avfuel Corporation | SIP softphones via 3CX system | A | USA - Nationwide | 313-789-1291 |
| AVH | Androscoggin Valley Hospital | PBX/PS911/Shared Tenant | A | NH | 603-723-9605 |
| AVILA | AVILA (CANCELLED) | PBX/Facilt | C | NY | 800-829-0420 |
| AVOIP | AT&T | CLEC Facility VoIP Provider | A | USA - Nationwide | 888-249-4980 |
| AVR | Avaria - CANCELLED | VoIP Reseller | C | USA - Nationwide | 919-559-9693 |