Telephony

Telephony is what connects your v3 agent to actual phone calls — inbound (a customer calls your number) and outbound (your bot calls a customer). Configure it in AI Agent → Voice → Telephony.

This page is about wiring up a telephony provider and routing calls. For making test calls without telephony, see Testing — the Voice Playground supports browser-based WebRTC calls.

Step 1: Open the Telephony page

In your bot, go to AI Agent → Voice → Telephony.

You'll see provider configuration cards for the supported telephony partners.

Step 2: Pick a provider

Yellow supports the major telephony providers. Common picks:

Provider	Strengths
Vonage	Strong global coverage, popular for international deployments.
Twilio	Wide adoption, deep documentation, strong developer ecosystem.

Other providers may be available for your region or account — check what cards are visible on the page.

If you already have a contract with a provider, use that one. Switching telephony providers later is more disruptive than switching almost any other component.

Step 3: Provide credentials

Each provider needs:

• Account credentials (e.g. Twilio Account SID + Auth Token, Vonage API key + secret).
• A phone number (your existing one, or one you provision through the provider).
• SIP / connection details if you're using SIP trunking.

Yellow auto-routes SIP traffic to the correct regional endpoint based on your bot's region. You don't need to configure region-specific SIP hosts manually — that's handled.

Best practice: keep credentials in a password manager and rotate them per Yellow's security guidelines. Don't paste production credentials into a chat or email.

Step 4: Configure inbound

For incoming calls (your customer dials your number, the bot picks up):

1. In your telephony provider's dashboard, route the phone number to Yellow's inbound webhook (the page shows the exact URL for your region).
2. Make a test call to confirm it lands on your bot.
3. Listen for the welcome message — that's your Welcome message from AI Agent → Profile → Profile Settings speaking through your configured voice.

If the call rings but no audio plays, the most common causes are:

• Webhook URL routed to the wrong region.
• Missing welcome action — set one in Profile Settings.
• Voice provider misconfigured — verify in Voice Settings.

Step 5: Configure outbound

Outbound calls let your bot ring a phone number — for collections, appointment reminders, surveys, sales follow-ups, etc.

1. Make sure the provider account is enabled for outbound.
2. Confirm the caller ID is set correctly — this is what the recipient sees.
3. Make a test outbound call from the Voice Playground — type a phone number and click Make call.

For programmatic outbound (triggering calls from a workflow or external system), Yellow exposes an outbound-call API. Talk to your account team about API access.

Step 6: Test the full path

Before going live:

• Test inbound — call your number from a phone, run through the golden path, confirm the bot recognizes you and responds in the configured voice.
• Test outbound — initiate a call from the Voice Playground to your own phone, take the call, confirm.
• Test escalation — trigger a Transfer Call tool. Confirm it forwards to the configured human destination cleanly. See Escalation tools.
• Test in the actual region — if you have a multi-region deployment, test in each region. Regional SIP routing is automatic but easier to verify with a real call.

Best practices

• Use the same provider per region. Mixing Twilio and Vonage in one deployment is doable but adds operational complexity for limited gain.
• Set caller ID thoughtfully. Recipients are more likely to pick up calls from a familiar local number; spam filters punish numbers without consistent usage patterns.
• Verify recording compliance for your region. Some jurisdictions require explicit consent before recording. Configure the Recording action on your Transfer Call tool accordingly. See Escalation tools.
• Don't publish your inbound webhook URL. Treat it like an API key.
• Have a fallback path. If Yellow can't reach the LLM, what does the user hear? A generic apology + a fallback to a human is far better than dead air. Wire the Fallback in Profile Settings to a human-handoff workflow.
• Keep a runbook. When something breaks at 2 a.m. (it will), you want a one-page runbook with: where credentials live, how to disable the bot temporarily, who to call. Don't write this during the incident.

Common pitfalls

Symptom	Likely cause
Calls ring but no audio	Webhook URL routed to the wrong region, or voice provider misconfigured.
Outbound calls fail silently	Provider's outbound permission disabled, or insufficient balance.
Recipient sees an unfamiliar caller ID	Caller ID not set or set to a number with poor reputation.
Audio is choppy or robotic	Codec mismatch on the SIP trunk, or bandwidth issues. Check the provider's documentation for recommended codec settings.
Some regions sound great, others terrible	Regional routing is fine; check whether some regions are using TTS providers with weaker support for that language. Switch provider per region in Voice Settings.

Reference for the rest

• Voice Settings — provider, voice, VAD per agent.
• Custom Voices — clone a brand voice for your calls.
• Testing — Voice Playground walkthrough.
• Voice as a Channel (cookbook) — foundational voice concepts and architecture.

Continue to: Testing.