SIP Trunk Pricing 2026: Cost Per Minute Across Twilio, Telnyx, Bandwidth, Plivo, Vonage, voip.ms & More

If you're running an AI voice agent at any meaningful volume in 2026, the SIP trunk underneath it is one of your three largest cost lines (alongside the LLM and the TTS). Pick the wrong trunk and you'll overpay by 5–20x. Pick the right trunk and the underlying voice carriage runs you $0.003–$0.008 per minute — at which point your AI orchestration, LLM, and TTS costs dominate the cost stack.

This guide compares SIP trunk pricing across the 12 providers most commonly used for AI voice deployments in 2026: Twilio, Telnyx, Bandwidth, Plivo, Vonage, voip.ms, Sinch, Vonage Business, SignalWire, 8x8, RingCentral, and wholesale carriers. We cover per-minute rates, DID rental, channel pricing, SMS, media streams (critical for AI voice), inbound vs outbound asymmetry, international rates, and how to pick the right trunk for your workload.

What SIP Trunking Actually Is (and Why AI Voice Needs It)

SIP (Session Initiation Protocol) trunking is the modern replacement for legacy PRI/T1 phone lines. A SIP trunk carries voice calls over the public internet to and from the PSTN (the traditional phone network), giving you a programmable, software-defined phone system instead of physical phone lines.

For AI voice agents specifically, the SIP trunk does five jobs:

1. Connects PSTN calls into your AI infrastructure — when a customer dials your business number, the SIP trunk delivers the call audio to your voice agent stack.
2. Places outbound PSTN calls from your AI agent — when your AI cold caller dials a prospect, the SIP trunk carries the outgoing leg to the prospect's carrier.
3. Provides DIDs (phone numbers) — local, toll-free, vanity — your inbound presence and your branded caller ID display register against numbers owned and routed by the trunk provider.
4. Carries STIR/SHAKEN attestation — for outbound calls to be attested as A-tier (not 'Spam Likely'), the trunk provider must support and sign the call.
5. Streams real-time audio for AI processing — modern AI voice agents need media streams (raw audio frames pushed to your STT/LLM in real time), not just SIP signaling. Twilio Media Streams, Telnyx Media Streaming, and similar features are what make AI voice possible on these trunks.

How SIP Trunk Pricing Works: Per-Minute, Per-Channel, Per-DID

SIP trunk providers bill across multiple line items. Confusion about which dimensions you'll actually use is the #1 reason teams overpay.

The pricing model that matters for AI voice: per-minute voice + per-minute media streams + per-DID monthly + per-message SMS. Channel-based pricing is a legacy model that doesn't fit AI workloads (where concurrent call count is highly variable). Avoid channel-based contracts unless your call pattern is steady-state.

2026 SIP Trunk Provider Comparison: 12 Providers Ranked

Patterns worth noting: Twilio is the most expensive but has the best developer experience and broadest feature coverage. Telnyx, Plivo, and SignalWire are clear Twilio alternatives at 40–60% lower cost with comparable APIs. Bandwidth and wholesale carriers are cheapest but require more technical depth. voip.ms is the budget pick for small business but lacks the AI features (media streams, STIR/SHAKEN automation) needed for production AI voice.

Twilio Cost Breakdown: Voice, SMS, Media Streams

Twilio is the most common starting point for AI voice deployments because its developer experience leads the category. How much does Twilio cost in practice for AI voice?

Practical example: an AI cold-calling deployment running 5,000 outbound minutes/month on Twilio costs roughly: $0.013 voice + $0.004 media streams = $0.017/min × 5,000 = $85/month just for the trunk. Add $11.50 for 10 DIDs, $50 for branded caller ID, and you're at ~$150/month in pure trunk costs — before any AI processing layer.

Compare that to Telnyx for the same workload: $0.005 voice + $0 media streams (included) = $0.005/min × 5,000 = $25/month + $10 DIDs = $35/month. Same call quality, ~75% cheaper. Telnyx API is comparable to Twilio in completeness and DX.

Wholesale SIP Trunk Pricing: When Volume Justifies It

Wholesale SIP trunk pricing from Tier-1 carriers (Inteliquent, Bandwidth Wholesale, Level 3/Lumen, Verizon Wholesale) lands at $0.003–$0.005/min for US voice — about half the retail rate from Twilio or Telnyx.

The catch: wholesale contracts typically require:

• Minimum monthly commit — usually $5,000–$25,000/month. Below this, retail is cheaper.
• Direct interconnect — your infrastructure has to connect to the wholesale carrier's network via dedicated peering or specific transit providers. You're not just hitting an API.
• Your own SBC (Session Border Controller) — wholesale doesn't bundle the call control layer. You run your own Kamailio, OpenSIPS, or commercial SBC.
• Engineering operations — wholesale relationships need active management. Carrier maintenance windows, DID porting issues, fraud monitoring, and CDR reconciliation are your problems.
• Compliance and STIR/SHAKEN attestation — you have to register as a service provider, attest your own calls, and handle complaints.

Practical rule: at under 100,000 outbound minutes per month, stay on retail SIP (Telnyx, Plivo, SignalWire). At 100,000–500,000/month, consider wholesale with a CPaaS reseller in front. At 500,000+/month, direct wholesale starts to pay off.

Inbound vs Outbound SIP Rates: The Asymmetry That Matters

Most providers charge differently for inbound vs outbound, and the asymmetry direction varies by provider:

• Twilio, Vonage: Inbound is cheaper than outbound. Outbound carries termination fees (paid to the destination carrier); inbound has lower per-minute cost.
• Bandwidth: Inbound and outbound nearly identical at scale; pricing depends on customer's negotiated commit.
• Toll-free DIDs (any provider): Inbound is significantly more expensive than local DID inbound — toll-free fees compensate the originating carrier.

Implication for AI voice workload design: an AI receptionist (mostly inbound) optimizes differently than an AI cold caller (mostly outbound). For receptionists, look at inbound per-minute first and DID rental second. For cold callers, outbound per-minute and media streams dominate. Toll-free inbound is the most expensive minute on most providers — use local DIDs unless you specifically need toll-free presence.

International SIP Trunking: Per-Country Rate Tables

International SIP rates vary 100x by destination. Quick reference (outbound, retail):

For international AI voice deployments, work with carriers offering region-specific routes (least-cost routing, LCR) rather than relying on a single global provider. Sinch and Bandwidth offer the strongest LCR optimization for global outbound.

Custom Toll-Free Numbers and Vanity DID Pricing

Custom toll-free numbers (1-800-FLOWERS, 1-800-CONTACTS-style vanity numbers) carry separate pricing dimensions:

• Standard toll-free DID (random): $1.00–$3.00/mo + per-minute inbound at higher rate.
• Vanity toll-free (custom word/digits): $25–$500/mo depending on memorability and availability. Premium vanities (8XX numbers spelling common words) can run $1,000+/mo or require purchase from the toll-free aftermarket.
• Vanity local DID (e.g., 1-415-RINGLYN): $20–$100/mo. Same rate structure but cheaper than vanity toll-free.
• Setup/porting fees: $25–$500 one-time per vanity number depending on current ownership.

Vanity numbers are a brand investment, not a cost optimization. For AI voice deployments where the AI books the conversation (not the caller-ID display), vanity numbers rarely improve outcomes enough to justify the premium. Spend the budget on branded caller ID registration instead — your business name displayed on the recipient's phone matters more than a memorable number.

How to Pick a SIP Trunk Provider for AI Voice Agent Workloads

1. Native media streams support. Non-negotiable for AI voice. Twilio, Telnyx, Plivo, Vonage, SignalWire, Sinch all support it. voip.ms, RingCentral, 8x8 do not (or have very limited support).
2. STIR/SHAKEN A-attestation. Must be supported and easy to enable. Twilio Trust Hub, Telnyx Trust Center, and equivalents at other providers.
3. API depth + documentation. Twilio leads, then Telnyx, then Plivo and SignalWire (both Twilio-API-compatible). The depth matters when your AI orchestration layer needs programmable call control.
4. Pricing transparency. Published per-minute rates are a green flag. Providers requiring 'contact sales' for basic pricing are usually expensive.
5. Regional reach. If you serve international callers, verify the provider's coverage in your target countries. Sinch and Bandwidth lead globally; Twilio is strong in EN-speaking markets.
6. Compliance posture. SOC 2 Type II audit, GDPR Data Processing Addendum, HIPAA-eligible products (for healthcare). All major providers offer these, but verify before contracting.
7. Outage history. Check the provider's status page history. Twilio, Telnyx, Bandwidth have all had multi-hour outages in the past 24 months. Multi-provider failover (active or warm-standby) is worth designing in for any business-critical deployment.
8. Or — skip all of this. Use a bundled AI voice platform (Ringlyn AI, Bland AI, Synthflow) that includes the SIP trunk in the per-minute rate. Skip the multi-vendor billing reconciliation.