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Bring Your Own SIP Trunk to a Voice AI Platform: How It Works

Bolti Team·

Telephony costs are the biggest variable in running a voice AI agent at scale — and most platforms lock you into their own numbers at their own rates. Bolti, a voice AI platform for production-grade phone agents (starting at ₹7/min with a free 50-minute trial), lets you bring your own SIP trunk (BYOC) so you control the carrier relationship, the per-minute rate, and the routing.

What Does "Bring Your Own SIP Trunk" Mean for Voice AI?

Bring Your Own Carrier (BYOC) means connecting your existing telephony infrastructure — a SIP trunk from Twilio, Plivo, Exotel, or any other provider — directly to the voice AI platform instead of using the platform's bundled numbers. The AI agent still handles the conversation; your trunk handles the call transport.

In practice, this means:

  • You negotiate your own per-minute rates with your carrier
  • You keep existing DID numbers and caller IDs your customers already recognise
  • You stay compliant with carrier agreements you've already signed
  • You avoid double-paying for telephony (your carrier + the platform's markup)

For teams running thousands of minutes a month, the difference between a platform's bundled rate and your negotiated trunk rate can be significant — often 30–60% of total operating cost.

How Bolti's BYOC Telephony Layer Works

Bolti treats telephony as one of four provider categories that power every call — alongside Speech-to-Text (STT), a Large Language Model (LLM), and Text-to-Speech (TTS). You configure each category independently, per agent.

The call flow looks like this:

  1. Inbound or outbound call arrives or is initiated via your SIP trunk
  2. STT transcribes the caller's audio in real time (Deepgram, Fennec for Indian languages, Azure, and others)
  3. LLM decides what the agent says next and which tools to call
  4. TTS synthesises the agent's voice and streams audio back
  5. Your SIP trunk carries that audio to the caller over PSTN

Bolti supports Twilio, Plivo, and Exotel as named integrations, and any standards-compliant SIP trunk via the BYOC configuration. If you already use Exotel for your support centre or Plivo for your outbound campaigns, you point Bolti at the same trunk.

What You Need to Set This Up

  • An active SIP trunk with your chosen carrier
  • SIP credentials (username, password, SIP URI or IP)
  • Inbound/outbound routing rules configured on the carrier side to point at Bolti's SIP endpoint
  • A Bolti workspace with telephony configured under agent settings

No specialised SIP engineering is required. The configuration is done through the Bolti dashboard — the same dashboard actions are also available as REST API calls if you want to automate provisioning.

Why BYOC Matters More Than Most Platforms Admit

When you're evaluating voice AI platforms, the headline per-minute rate rarely tells the full story. Platforms that bundle telephony typically charge a blended rate that includes a carrier margin. As call volume grows, that margin compounds.

Here's what BYOC actually changes:

  • Cost predictability. Your carrier invoice is separate from your AI platform invoice. You can optimise each independently.
  • Number portability. Keep the 1800 or 022-XXXX numbers your customers already call. No re-registration, no brand disruption.
  • Regulatory control. Some industries (BFSI, healthcare) require calls to stay on specific carriers or within specific geographies. BYOC lets you enforce that.
  • Failover flexibility. If one carrier has an outage, you can reroute at the trunk level without touching your AI agent configuration.
  • Existing contracts. If you've negotiated volume discounts with Exotel or Plivo, those discounts apply to your AI call traffic too.

Competitors like Bolna AI primarily offer platform-managed telephony. If carrier flexibility is a requirement — especially for enterprises with existing trunk agreements — that's a meaningful gap.

BYOC in the Context of Bolti's Full Provider Architecture

Bolti's provider model is worth understanding because BYOC is one lever among several. Every agent independently selects:

  • STT provider — Deepgram, Fennec (optimised for Hindi, Tamil, Telugu, and other Indian languages), AssemblyAI, Azure, ElevenLabs, Cartesia
  • LLM — OpenAI, Gemini, Groq, DeepSeek, or open-source models via Baseten (Llama 4, Qwen3, DeepSeek-V3.1)
  • TTS provider — multiple providers with preview-able voice cards across 80+ languages
  • Telephony — Bolti-managed numbers or your own SIP trunk

This means you're not forced into a single vendor's stack. A team running Hindi outbound sales calls might use Fennec for STT (better accent handling), DeepSeek-V3.1 on Baseten for cost-efficient LLM inference, an Anushka-voice TTS card, and their existing Exotel trunk — all configured per agent.

See how Bolti handles telephony for outbound sales for a worked example of this provider mix in production.

Enterprise Considerations: Security and Compliance

For enterprise deployments, BYOC pairs with Bolti's broader data protection controls:

  • PII redaction at runtime — sensitive caller data (card numbers, Aadhaar references, account IDs) is masked before it reaches the LLM, regardless of which carrier delivers the call
  • Encrypted audio path — real-time audio between the SIP carrier, Bolti's agent runtime, and the TTS layer is encrypted in transit
  • On-premises deployment — available for organisations that need the entire stack inside their own infrastructure
  • DPDP/GDPR/HIPAA-aligned contracts — Bolti's data processing agreements cover regulated industries

These controls apply whether you use Bolti-managed numbers or your own trunk. BYOC doesn't weaken the security posture — it just moves the carrier relationship to your side of the boundary.

Set Up Your First BYOC Agent on Bolti

If you have an existing SIP trunk with Twilio, Plivo, or Exotel, you can connect it to a Bolti voice agent in under 15 minutes. Bolti's free trial includes 50 minutes of call time — enough to run a real test campaign on your own trunk before committing to ₹7/min pay-as-you-go. Connect your SIP trunk and start your free trial to see exactly what your per-minute cost looks like when telephony is yours to control.

Frequently Asked Questions

Which SIP trunk providers does Bolti support for BYOC?

Bolti supports Twilio, Plivo, and Exotel as named integrations, plus any standards-compliant SIP trunk. You configure the trunk credentials in the telephony section of your agent settings.

Can I keep my existing phone numbers when using Bolti?

Yes. With BYOC, your DIDs (Direct Inward Dialing numbers) stay with your carrier. Bolti routes calls through your trunk, so your existing 1800 or local numbers continue to work without re-registration.

Does BYOC affect Bolti's PII protection or call encryption?

No. PII redaction at runtime, encrypted audio in transit, and all other data protection controls apply regardless of whether you use Bolti-managed numbers or your own SIP trunk.

How does Bolti's BYOC compare to Bolna AI's telephony options?

Bolna AI primarily offers platform-managed telephony. Bolti's BYOC lets you bring your own Twilio, Plivo, or Exotel trunk, which means you keep negotiated carrier rates and existing number inventory rather than paying a platform-managed rate.

What does it cost to use Bolti with my own SIP trunk?

Bolti's AI platform usage is priced at ₹7/min pay-as-you-go. With BYOC, your carrier's per-minute rate is billed separately by your carrier — Bolti does not add a telephony markup on top of your own trunk.