Phone Numbers for Vapi, Retell and ElevenLabs Agents [2026]

Short answer: you do not need AgentCall to give a Vapi, Retell, or ElevenLabs agent a voice number. All three can attach one themselves. Where AgentCall helps is everything around the voice call: a number that also receives texts and one-time codes, a hosted MCP server your coding agent can drive, caller memory, and a managed AI voice for the cases where you do not need a separate voice platform at all.

What Vapi, Retell, and ElevenLabs Already Do for Phone Numbers

Older guides, including an earlier version of this one, say these platforms leave you to find your own phone number. That is no longer true, so here is the current picture, checked against each vendor's public docs:

• Vapi offers free US numbers for voice (up to 10 per account) and lets you import numbers from Twilio and other providers.
• Retell lets you buy numbers inside its dashboard (listed at about $2/month each) or connect your own through SIP.
• ElevenLabs Agents imports Twilio numbers natively and connects to any provider that speaks SIP trunking.

Vendor pricing and limits change often, so confirm on their pricing pages before you commit. The point is that voice numbers are a solved problem on those platforms, and we would rather say so than pretend otherwise.

Where AgentCall Fits Next to a Voice Platform

These are the jobs a voice platform does not do for you, and where an AgentCall number earns its place:

• Receive texts and pull out one-time codes (live OTP extraction needs Pro)
• Give every agent in your app its own isolated number, inbox, and webhooks
• Let your own agent text you back through relay mode, with STOP handling done for you
• Remember callers across calls, so the next brief mentions the last conversation
• Expose all of it over a hosted MCP server at api.agentcall.co/mcp

One honest limit: an AgentCall number is not a SIP trunk. AgentCall does not hand a live call's audio to Vapi, Retell, or ElevenLabs. If you want one of those platforms to speak on a call, attach a number inside that platform. If you want AgentCall to speak, use its built-in AI voice.

Pattern 1: Text From AgentCall, Talk From Your Voice Platform

Provision an AgentCall number for SMS, point a webhook at your backend, and start a voice call on your platform when a text arrives. Sign up at agentcall.co/sign-up, then provision a number:

curl -X POST https://api.agentcall.co/v1/numbers/provision \
  -H "Authorization: Bearer ac_live_your_key" \
  -H "Content-Type: application/json" \
  -d '{"country": "US", "type": "local"}'

Register a webhook for inbound texts. Deliveries arrive as { event, timestamp, data } with an X-AgentCall-Signature header you should verify:

curl -X POST https://api.agentcall.co/v1/webhooks \
  -H "Authorization: Bearer ac_live_your_key" \
  -H "Content-Type: application/json" \
  -d '{"url": "https://my-backend.com/agentcall", "events": ["sms.inbound"]}'

Your handler then starts a Vapi call. This uses Vapi's POST /call with an assistant and a Vapi phone number you already own there:

app.post("/agentcall", async (req, res) => {
  const { event, data } = req.body;
  if (event !== "sms.inbound") return res.json({ ok: true });

  // A customer texted "call me". Ring them from your Vapi number.
  await fetch("https://api.vapi.ai/call", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${process.env.VAPI_API_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      assistantId: process.env.VAPI_ASSISTANT_ID,
      phoneNumberId: process.env.VAPI_PHONE_NUMBER_ID,
      customer: { number: data.from },
    }),
  });

  res.json({ ok: true });
});

The same shape works for Retell (create-phone-call with your Retell from_number) and ElevenLabs agents. Check each vendor's current API reference for the exact fields, since they change quickly.

Pattern 2: Let the Voice Agent Call AgentCall as a Tool

All three platforms support server tools or function calls during a conversation. Point one at an endpoint you host, and have that endpoint use the AgentCall SDK. For example, a tool that texts the caller a confirmation while the call is still live:

import AgentCall from "agentcall";

const agentcall = new AgentCall(process.env.AGENTCALL_API_KEY);

app.post("/tools/send-confirmation", async (req, res) => {
  const { to, text } = req.body;
  const message = await agentcall.sms.send({
    from: process.env.AGENTCALL_NUMBER, // your provisioned +1 number
    to,
    body: text,
  });
  res.json({ result: `sent ${message.id}` });
});

Texts to new destinations are restricted during a live trial (five attempts to verified destinations), so plan on Pro for production use.

When to Skip the Voice Platform Entirely

AgentCall also runs the AI voice itself. Configure a number once and inbound calls are answered by a managed voice agent that follows your system prompt and returns a transcript. For outbound, pass a system prompt, a first message, and a destination. Outbound AI calls need Pro:

curl -X POST https://api.agentcall.co/v1/calls/ai \
  -H "Authorization: Bearer ac_live_your_key" \
  -H "Content-Type: application/json" \
  -d '{
    "to": "+12125550100",
    "from": "+13145550123",
    "systemPrompt": "You are a friendly appointment scheduler for Acme Dental...",
    "firstMessage": "Hi, this is Alex calling from Acme Dental."
  }'

That covers appointment reminders, lead qualification, and surveys. If you need deep control of voice characteristics, turn-taking tuning, or a visual flow builder, a dedicated voice platform is the better fit, and you can still use AgentCall alongside it as described above. If you want a more natural voice without a second vendor, see Premium Voice.

Pricing Recap

• New accounts receive a one-time 72-hour live trial with one US/Canada local number, 300 managed inbound AI seconds (five minutes) total, and five SMS send attempts to verified destinations. Card verification is required before number allocation; the clock starts when allocation succeeds. There is no monthly reset or automatic paid subscription. Live OTP extraction and outbound calls require Pro.
• Pro is $19.99/month plus number rental and usage: local numbers $2/month each, toll-free $2.50/month, outbound SMS $0.015/message, standard outbound voice $0.035/min, managed AI voice $0.40/min, BYOK voice $0.10/min plus your AI provider's charges, or Premium Voice $0.59/min. AI calls round up to whole minutes per call. New-account destination/business verification can still apply after upgrading.

Next Steps

• Sign up and provision your first phone number
• Voice AI Infrastructure: Phone Numbers for AI Voice Agents
• 5 Best Phone APIs for AI Agents in 2026
• How to Give Every AI Agent Its Own Phone Number
• AgentCall vs Twilio: Why You Don't Need an Inbound Webhook to Answer Calls
• Full API documentation

Questions? Email us at support@agentcall.co.