A SIP trunk for AI voice agents is the carrier connection your bots dial out on. VoiceOI's outbound bots call through the trunk you already have: Twilio Elastic SIP Trunking, Telnyx or any SIP carrier, added by pasting one sip.conf or pjsip.conf block into the Carrier Manager. Your carrier bills the minutes; VoiceOI bills per bot.
SIP (Session Initiation Protocol) is how internet phone systems set up and end calls. A SIP trunk is the carrier service that connects a system like VoiceOI to the public phone network, so it can ring any phone number.
For an AI voice agent, the trunk is the way out. The campaign hands each call to your carrier, the carrier rings the lead, and once someone answers, the audio flows over the trunk between that person and the bot. When the lead qualifies, the bot transfers the live call to a human closer over SIP.
VoiceOI runs the bots and the conversation on its hosted platform; the trunk stays yours, with your carrier account, numbers and rates. You can run bots two ways: VoiceOI's built-in dialer runs bot campaigns through the carrier you add, with no VICIdial needed, or the bots join your existing VICIdial campaigns as remote agents.
Dial
The campaign dials the next lead inside your calling window.
Trunk
The call goes out through your SIP carrier.
Answer
A machine answering ends the call, logged as AM.
Talk
The bot asks your qualifying questions.
Transfer
Fronter and closer tiers only: qualified leads go live to a closer with AI notes.
Log
Dispositions, recordings and transcripts are available for review.
VoiceOI handles every carrier the same way: as a SIP trunk defined by a sip.conf or pjsip.conf block. These are the common setups.
| Setup | How it connects | Guide |
|---|---|---|
| Twilio Elastic SIP Trunking | Create a trunk with a termination SIP URI and credentials in your Twilio account, then add it in the Carrier Manager. | Twilio SIP trunk for AI voice agents |
| Telnyx | Create a SIP connection with an Outbound Voice Profile in your Telnyx account, then add it in the Carrier Manager. | Telnyx SIP trunk for AI voice bots |
| Any other SIP carrier | Paste the carrier's sip.conf or pjsip.conf block into the Carrier Manager. | The setup steps below |
| Asterisk or FreePBX | Asterisk and FreePBX-based systems connect to VoiceOI over SIP. | Asterisk AI voice bot |
| VICIdial | Bots join your campaigns as remote agents and write dispositions back; VICIdial keeps your lists and reports. | VICIdial AI integration |
Setup happens in two places: your carrier's portal and VoiceOI's Carrier Manager. Most of the work is collecting the right details from the carrier.
You need the SIP server address or domain, how the carrier authenticates you (a username and password, allowed IP addresses, or both), the caller-ID numbers you may send, and the number format it expects. Twilio and Telnyx both expect E.164 numbers with a leading plus, such as +12125550123.
Add a carrier, paste its sip.conf (chan_sip) or pjsip.conf (PJSIP) block and save it. If the trunk already runs on VICIdial, copy the settings your VICIdial carrier uses.
Build the call flow in the no-code voice bot builder, as a recorded-voice bot or an AI agent, and run it in the simulator before it calls anyone.
Upload a CSV with only your own phone number, set up the campaign to dial through the carrier you added and start it. Check that the call rings, shows the right caller ID and appears in the call log, then review its recording and transcript.
Load your leads, set pacing within your carrier's limits, add calling windows and retries, and watch the calls in the realtime view. The outbound AI campaign manager covers scheduling in more detail.
Carrier number-format requirements from Twilio's Elastic SIP Trunking docs and Telnyx's Asterisk guide, reviewed October 2026.
The trunk carries the audio; the bot decides what happens on the call. This is what each call gets.
When a machine picks up, the bot hangs up and logs the call as AM, so closers never get a voicemail greeting. VoiceOI does not leave messages.
A recorded-voice bot follows your branching script word for word; an AI agent works inside the questions and rules you set. Replies took about a second per turn in testing.
When someone asks not to be called, the bot ends the call and records the outcome. Machine and DNC phrase lists are editable per organization.
Qualified leads are handed to a human closer over SIP with AI-written notes, using your routing rules. The bot does not stay on the line to introduce the caller.
Campaigns work through your list with the pacing, retries and timezone-aware calling windows you set. Read more about AI live transfer and answering machine detection for call centers.
Your carrier bills you directly for minutes, phone numbers and any carrier features, under your own agreement with them. VoiceOI bills separately: a prepaid price per bot per month, with no per-minute AI fee. Volume discounts count concurrent bots (seats), so the number of bots you plan to run at once is also the number to give your carrier.
Speech recognition, voices and the language model run on VoiceOI's infrastructure by default. Bots are priced per bot per month by tier: Hosted SIP tiers list from $45 to $155 and VICIdial / Asterisk tiers from $25 to $135. The Hosted SIP tiers are listed below; the pricing page shows which tier applies to your setup.
| Bot tier | Question limit | Includes | List price | Floor after discounts |
|---|---|---|---|---|
| SIP Simple Fronter | Max 3 Questions | Basic filtering, No Closer comments, Live Transfers, Dedicated Switch | $45 per bot/month | $28 per bot/month |
| SIP Good Fronter | Max 5 Questions | Verifies Age/Zip, Leaves comments for Closer, Live Transfers, Dedicated Switch | $55 per bot/month | $34 per bot/month |
| SIP Simple LG | Flexible Question Flow | Generative AI, No Google Sheets export, No Live Transfers, Dedicated Switch | $70 per bot/month | $45 per bot/month |
| SIP Pro LG | Flexible Question Flow | Generative AI, Google Sheets export, No Live Transfers, Dedicated Switch | $85 per bot/month | $55 per bot/month |
| SIP Standard Closer | Up to 12 Questions | Live Transfers, Call Termination on Transfer, Dedicated Switch | $120 per bot/month | $75 per bot/month |
| SIP Ultimate Closer | Extended Question Flow | Complex branching, Live Transfers, Call Termination on Transfer, Dedicated Switch | $155 per bot/month | $95 per bot/month |
In the table, Dedicated Switch means hosted SIP bots run through a switch dedicated to the bots, rather than through your own VICIdial or Asterisk system. Call Termination on Transfer means when a bot transfers a qualified call, the bot ends its side of the call and moves on to the next call while the closer takes the transferred call. Volume discounts: 15% Off (10-49 Seats), 30% Off (50-99 Seats), 45% Off (100-249 Seats), 60% Off (250+ Seats). No tier drops below its floor. Bots that connect to your own VICIdial or Asterisk system are listed on the VICIdial / Asterisk tiers, from $25 to $135 per bot per month. See AI voice bot pricing, the voice AI cost comparison and AI calling cost per minute.
Carriers differ more than their rate cards suggest. These answers decide how many bots you can run, how fast you can dial and how your calls show up on people's phones. They are questions for your carrier, not VoiceOI settings. Our SIP trunk selection guide turns them into seven sourced checks.
Size the trunk for the most calls you want live at once, and tell the carrier how many bots you plan to run at the same time. Telnyx, for example, says a 403 on outbound calls usually means the connection hit its channel limit.
CPS caps how fast new calls can start. Twilio starts each trunk at 1 CPS per region and rejects calls above the limit.
Twilio ties CPS increases to an average call length over 30 seconds, no more than 10% of calls at 12 seconds or less, and an answer-seizure rate above 70%. Short calls, such as machines the bot hangs up on, count toward numbers like these.
Usually a username and password, allowed IP addresses, or both. Twilio requires at least one and recommends credentials; Telnyx offers credentials, IP or FQDN authentication. The block you paste into VoiceOI has to match.
Twilio accepts only a Twilio number on your account or a verified caller ID, with numbers in E.164 format, and rejects calls that break those rules.
US providers sign calls at one of three levels: A (full: the provider knows the caller and has verified its right to use the number), B (partial: it knows the caller but not the number) or C (gateway). Ask which level your numbers will carry, and what the carrier can do if one gets labeled as spam.
Ask for the rates to the places you call, the billing increment and any per-call minimum. Short calls add up on large outbound lists.
Read the acceptable-use policy before you load a list: Twilio lists breaking its Terms of Service or Acceptable Use Policy among the reasons calls get declined. Ask about spend controls too; Telnyx lets you restrict destinations and set a daily spend limit per connection.
Examples from Twilio's CPS guide, Elastic SIP Trunking docs and troubleshooting guide, Telnyx's SIP trunk setup guide, and FCC order 24-120, all reviewed October 2026.
The trunk carries whatever you dial, so consent and calling rules stay with you. Since the FCC's February 2024 ruling, AI-generated voices count as “artificial” voices under the TCPA, so telemarketing calls that use them need the called person's prior express written consent (FCC news release). You remain responsible for your own compliance, and nothing on this page is legal advice.
VoiceOI's controls support that work: spoken do-not-call requests end the call, calls can include an optional TCPA AI-voice disclosure, campaigns use timezone-aware calling windows, and calls are recorded and transcribed for review. See TCPA controls for AI voice bots and do-not-call (DNC) controls.
Paste your carrier block, build a bot in the no-code builder and test it in the simulator before it dials a single lead.
Common questions about running VoiceOI bots on your own SIP carrier.
Yes. Any SIP carrier can be added by pasting its sip.conf or pjsip.conf block into the Carrier Manager, including Twilio Elastic SIP Trunking and Telnyx. A VICIdial shop can reuse the settings of the carrier it already runs.
That depends on your carrier account. On Telnyx you set a channel limit per connection; Twilio's US price list includes unlimited call concurrency, though trial accounts are limited to 4 concurrent calls, and upgraded accounts without an approved Business Profile can hit the same 4-call error. A separate calls-per-second limit caps how fast new calls can start. On the VoiceOI side, volume discounts count concurrent bots (seats), so tell your carrier how many bots you plan to run at once.
No. VoiceOI is built for outbound campaigns: bots place calls and transfer qualified leads to your closers. It isn't an inbound receptionist or a call-routing IVR.
Concurrency limits from Twilio's US pricing page, troubleshooting guide and Telnyx's SIP trunk setup guide, reviewed October 2026.
Third-party details on this page come from these pages, reviewed October 2026. Prices, limits and console labels change often, so check the source before you rely on them.