| CoID | Company | Type | Status | States Served | 24X7 Phone |
| TONEC | Tone Communication Services LLC | CLEC Reseller | A | USA - Nationwide | 800-515-8182 |
| TONM | Town of New Milford | PBX/PS911/Shared Tenant | A | CT | 860-898-0282 |
| TOPNY | Town of Orchard Park - CANCELLED | VoIP Provider | C | NY | 716-662-6444 |
| TOPS | Topsham Telephone Company | CLEC Facility CLEC Reseller CLEC UNE ILEC | A | NH | VT | 802-439-5325 |
| TOS | Town of Scituate | PBX/PS911/Shared Tenant | A | MA | 781-545-1212 |
| TOT | Town of Thornton | PBX/PS911/Shared Tenant | A | USA - Nationwide | 603-726-8168 |
| TOTAH | Totah Communications Inc. | ILEC | A | OK | KS | 918-697-7871 |
| TOTEL | Totelcom Networks LLC | CLEC Facility | A | TX | 254-842-7039 |
| TOUS | TOUS SOFTWARE CORP | VoIP Reseller VoIP Provider | A | USA - Nationwide | 954-809-3100 |
| TOW | Town Of Wayland - Wayland Public Schools - CANCELLED | PBX/PS911/Shared Tenant | C | MA | 508-358-4747 |
| TOWCT | Town of Westport | VoIP | A | CT | 203-341-5010 |
| TP01 | Talking Platforms LLC. | VoIP Reseller | A | USA - Nation Wide | 202-747-0066 |
| TPAC | Telepacific Communications | CLEC Facility | CLEC Reseller | A | CA | NV | 800-851-6705 |
| TPS | Two Port Support LLC | PBX/PS911/Shared Tenant VoIP Reseller VoIP Provider | A | USA - Nationwide | CT | MA | NH | NY | RI | VT | 860-422-4600 |
| TRAN | Trans-Cascades Telephone Co. | Facility | A | OR | 503-630-4202 |
| TRAPP | Trapp Technology - CANCELLED | VoIP Provider | C | USA - Nationwide | 602-443-9145 |
| TRCL | Three River Communications | CLEC Facility | A | NE | 402-569-2666 |
| TRCNY | TC Wireless Inc. | CLEC Facility | A | KS | 620-767-5153 |
| TRCTC | Three River Community-Tech College (Cancelled) | PBX | C | CT | 886-885-2327 |
| TRDO | Intrado Life & Safety Inc. | VPC | A | USA - Nation Wide | 800-586-1062 |
| TRE | Tim Ron Enterprises LLC | Facility | A | Longview | TX | 903-230-0029 |
| TREST | Tresta Communications Inc. | VoIP Provider | A | USA - Nationwide | 844-287-3782 |
| TRICO | Ritter Communications - CANCELLED | Co-Op/Rural ILEC Internet Protocol Relay Provider VoIP Provider | C | AR | 870-974-9100 |
| TRIDA | Tridacom IT Solutions Inc. | VoIP Reseller VoIP Provider | A | USA - Nationwide | 1-647-478-1960 |
| TRIMO | Triangle Communication System Inc. | Wireless/Cellular/PCS | A | MT | 406-394-7807 |
| TRINE | Trine University | PBX/PS911/Shared Tenant | A | USA - Nation Wide | 260-665-4275 |
| TRIOS | RCCH Trios Health | PBX/PS911/Shared Tenant | A | WA | 509-221-5884 |
| TROWE | T. Rowe Price Associates Inc. | PBX/PS911/Shared Tenant | A | USA | 410-345-5111 |
| TROYC | Troy Cablevision Inc. | CLEC Facility | A | AL | 800-735-9546 |
| TRTC | The Rye Telephone Company | ILEC | A | CO | 719-676-3131 |
| TRTEL | Cingular Wireless (Cancelled - see ATTMO) | Wireless | C | ALL | 800-635-6840 |
| TRTL | Three River Telco | ILEC | A | NE | 402-569-2666 |
| TRTN | Triton PCS, Inc.-Mid-Atlantic Region (Cancelled) | Wireless | C | VA, TN | 888-663-6230 |
| TRU | Trumansburg Telephone Company Inc. | ILEC | A | NY | 866-353-7209 |
| TRU1 | The Arnold Companies | PBX/PS911/Shared Tenant | A | USA - Nationwide | 903-334-7974 |
| TRUE | True On Inc | VoIP Provider | A | CA | 619-650-0028 |
| TRUID | TRUSTID Inc | VoIP Provider | A | USA - Nationwide | 703-547-6008 |
| TRULY | Truly Technologies Inc | VoIP Provider | A | USA - Nationwide | 855-976-8759 |
| TRUPH | 1Global | Wireless/Cellular/PCS VoIP Provider | A | USA - Nationwide | 347-227-1599 |
| TRVGA | Truvista Communications of Georgia LLC | CLEC Facility | VoIP Provider | A | GA | 800-768-1212 |
| TRVRG | Trivergent State Communications (Cancelled - See NUVOX) | Facility, Reseller | C | NC, SC, GA, FL, AL, MS, LA, TN, KY | 800-800-9681 |
| TRVT | Twin Rivers Valley Telephone(Cancelled) | Reseller | C | IA | 515-379-1070 |
| TSCAN | Telescan Inc. - CANCELLED | CLEC Facility | VoIP | C | TN | 423-282-5043 |
| TSCC | TSC Communications Inc. | CLEC Facility ILEC VoIP Provider | A | OH | 419-739-2201 |
| TSCOP | The Solution Center - CANCELLED | VoIP Provider | C | USA - Nationwide | 708-403-9000 |
| TSEDV | Telephone Systems Efficiency Inc. | VoIP Provider | A | CT | ME | MA | NH | RI | VT | 603-493-8999 |
| TSG | The Schofield Group LLc - CANCELLED | PBX/PS911/Shared Tenant | C | USA | 978-597-0005 |
| TSGG | TSG Global Inc. - CANCELLED | Internet Protocol Relay Provider | C | USA - Nationwide | 877-662-8744 |
| TSH | Touchmark on South Hill | PBX/PS911/Shared Tenant | A | OR | WA | 509-536-2929 |
| TSI | Tech Strategies Inc. | VoIP Reseller | A | USA - Nationwide | 208-944-0031 |