TL;DR (for buyers and MSPs)
Market demand is growing across SIP trunking, CPaaS, and voice AI. That matters because more voice traffic is being embedded into software workflows, not just phone systems.
Viirtue is built for modern providers and MSPs who want carrier-grade SIP trunking that connects to PBXs, AI voice platforms, and CRMs, plus the operational tooling to actually sell and bill it correctly.
If you are developer-first and building custom voice apps, Twilio, Telnyx, and Bandwidth are common shortlist options depending on your architecture and procurement style.
If you are searching for the best SIP trunk providers, you are probably trying to do one (or more) of these:
Connect a PBX or contact center to the PSTN with reliable inbound and outbound calling
Add PSTN calling to AI voice agents (for example, ElevenLabs Agents)
Enable real phone calling inside CRMs for click-to-call, call logging, and automated workflows
The short version: SIP trunking is no longer “telecom plumbing.” In 2026, it is the backbone for PBX deployments, BYOC for UCaaS and CCaaS, and the fastest path to production-grade PSTN access for AI agents.
Market research: why this category is getting hotter
A “best SIP trunk provider” decision used to be mostly about per-minute rates and basic uptime. Now it is tied directly to growth in embedded communications and AI-led calling.
Here are a few directional data points to anchor what is happening:
SIP trunking growth: Mordor Intelligence estimates the SIP trunking market grows from $73.14B (2025) to $85.07B (2026) and to $181.58B (2031) (16.38% CAGR over 2026–2031).
Sizing varies by definition: ResearchAndMarkets (different scope) pegs SIP trunking services at $14.6B (2025), growing to $31.7B (2034) (9% CAGR). Translation: market size depends heavily on what each firm includes (pure services vs bundled UC and managed layers).
CPaaS tailwind: Technavio forecasts the CPaaS market will increase by $34.22B from 2024–2029 at a 24.6% CAGR, reflecting the shift toward API-first embedded communications.
AI in calling operations is scaling: Grand View Research estimates the call center AI market at $1.99B (2024), reaching $7.08B (2030) (23.8% CAGR).
Voice AI agents are accelerating: Technavio sizes voice AI agents as growing by $10.96B from 2024–2029 at 37.2% CAGR, which is one reason more teams now need production-ready PSTN connectivity for agents.
What this means in plain English: more companies are routing voice through software. That makes SIP trunking selection less about “can we connect a PBX” and more about “can we power PBX + AI + CRM workflows without breaking reliability, compliance, and billing.”
What is a SIP trunk provider?
A SIP trunk is what connects your PBX, contact center, or AI voice platform to the public telephone network (PSTN) so you can place and receive calls to real phone numbers. Viirtue summarizes it simply: a SIP trunk connects your PBX, contact center, or AI voice platform to the PSTN.
Twilio describes Elastic SIP Trunking similarly as connectivity for an IP-based communications infrastructure to connect to the PSTN.
Buying checklist: how to evaluate the best SIP trunk providers
Use this list if you want to choose correctly the first time.
1) Network reliability and call quality
Look for redundancy, smart routing, and proven operations under load. “Carrier-grade” should translate into consistent origination/termination, stable routing, and support processes that work when things go sideways.
2) Integration surface area
Your trunk should support what you deploy today and what you will deploy next:
PBXs and SBCs (on-prem, hosted, hybrid)
Contact centers and BYOC models
AI agent platforms that support SIP
CRM calling workflows (click-to-call, call logging, triggers)
3) Security and control
At minimum, you should be planning for TLS/SRTP support and tight routing controls (IP allowlists, SBC best practices, fraud guardrails). ElevenLabs’ SIP trunking documentation also references options like TLS transport and media encryption, reinforcing that “AI calling” still needs enterprise-grade telephony security fundamentals.
4) Compliance readiness
Caller ID authentication and robocall mitigation are no longer “nice to have.” The FCC describes STIR/SHAKEN as a caller ID authentication framework and maintains requirements tied to certifications and mitigation programs.
5) Operational fit (this is where MSPs win or lose)
If you are an MSP or reseller, the “best” trunk is the one you can:
quote quickly
provision repeatably
rate usage accurately
invoice cleanly
apply telecom taxes correctly
support without heroics
This is exactly why platform + trunk matters, not just trunk.
Best SIP Trunk Providers: top options for 2026 (Viirtue + 3 alternatives)
1) Viirtue (best for MSPs and providers selling PBX + AI calling + CRM workflows)
Best for: MSPs, telecom resellers, and modern providers who want carrier-grade SIP plus the operating system to scale it under their brand.
Viirtue’s SIP trunking is positioned for modern providers and explicitly calls out connectivity from PBX, contact center, or AI voice platform to the PSTN, along with features like multi-carrier and STIR/SHAKEN support.
Where Viirtue stands out for MSPs is that it is not “just dial tone.” It is dial tone plus a real quote-to-cash backbone:
ViiBE (quote-to-cash and orchestration): built to quote, rate, bill, and collect for telecom and voice AI use cases.
Automated usage rating: designed for both traditional voice and high-volume AI agent calling.
Telecom tax automation: automated telecom tax calculations inside the platform.
Why Viirtue fits the “PBX + AI + CRM” reality
PBXs: The trunk connects your PBX to the PSTN, supporting standard SIP interoperability patterns for MSP deployments.
AI agent platforms (example: ElevenLabs): ElevenLabs supports SIP trunking, so teams can connect existing telephony infrastructure to ElevenLabs Agents and keep phone numbers and routing logic.
CRMs: When your PSTN layer is stable, CRM calling becomes a workflow problem (click-to-call, logging, automation), not a reliability problem.
If you are productizing voice and AI calling, Viirtue’s model is designed to keep the “unsexy parts” (rating, taxes, invoicing) from becoming the bottleneck.
2) Twilio Elastic SIP Trunking (best for developer-first voice builds)
Best for: software teams building programmable voice and custom calling flows.
Twilio describes Elastic SIP Trunking as a cloud-based solution providing PSTN connectivity for IP-based communications infrastructure.
It also offers configuration guides specifically aimed at connecting IP-PBXs, contact centers, SBCs, and UC environments.
Considerations: Twilio is excellent if your differentiation is software and you have engineering resources. If you are reselling voice at scale as an MSP, you may still need a separate quote-to-cash and tax-compliance stack.
3) Telnyx SIP Trunks (best for API-first teams that want a private-network posture)
Best for: builders who want SIP trunks with programmatic control and a private IP network positioning.
Telnyx positions its SIP trunking as running on a private network with APIs and global scale.
Extra relevance for AI calling: ElevenLabs has documentation that walks through connecting Telnyx telephony components in the ElevenLabs agent workflow, reinforcing Telnyx as a common building block for AI PSTN calling deployments.
4) Bandwidth SIP Trunking (best for enterprise and carrier-style deployments)
Best for: enterprises and larger implementations that want a carrier-style provider and global reach.
Bandwidth positions SIP trunking for enterprises and notes coverage in 65+ countries, plus it highlights common use cases like powering voice inside UCaaS and CCaaS environments.
Considerations: Depending on your org size, procurement and implementation may be more enterprise-oriented than self-serve options.
Comparison table: Viirtue vs the 3 alternatives
Provider | Best for | Strengths | Watch-outs |
|---|---|---|---|
Viirtue | MSPs and providers selling PBX + AI calling + CRM workflows | Carrier-grade SIP + quote-to-cash (usage rating, tax automation), built for resale | Best value shows up when you monetize voice and need operations, not just connectivity |
Twilio | Developer-first voice apps | Strong docs, APIs, elastic scale | MSPs often need additional billing/tax tooling |
Telnyx | API-first teams | Private network positioning, programmatic control | You still own more of the “business system” work |
Bandwidth | Enterprise | Carrier-style reach and enterprise SIP focus | Can feel heavier vs self-serve models |
How Viirtue supports PSTN calling for AI agents (example: ElevenLabs)
AI voice agents are only “real” to customers when they can place and receive calls from real phone numbers.
ElevenLabs’ SIP trunking docs state SIP trunking allows you to connect your existing telephony infrastructure directly to ElevenLabs Agents and leverage ElevenLabs voice AI while keeping your phone system.
ElevenLabs also published an update about upgraded SIP integration that emphasizes maintaining existing phone numbers and routing logic, and mentions connecting to VoIP providers such as Twilio and Telnyx.
Where Viirtue fits: Viirtue’s trunk is designed to connect an AI voice platform to the PSTN, and ViiBE is designed to handle usage rating and taxes that show up fast when AI agents generate high call volumes.
Practical deployment patterns (PBX, AI, CRM)
Pattern A: PBX-first, AI as an add-on
PBX handles business logic (IVR, queues, extensions)
Route specific DIDs or call paths to AI agents (after-hours, overflow, scheduling)
Keep your existing numbering plan and migrate gradually
Pattern B: AI-first, PBX as the fallback
AI agent takes first contact
Escalate to the PBX queue or live agent when needed
Best for high-volume inbound lines
Pattern C: CRM-driven outbound calling
Trigger outbound calls from CRM sequences (lead follow-up, appointment confirmations)
Log outcomes and recordings to the CRM
Use SIP trunking as the stable PSTN layer underneath
Final Thoughts: Choosing the Best SIP Trunk Providers for 2026 and Beyond
Selecting the best SIP trunk providers in 2026 is no longer just a technical decision. It is a growth decision. The right provider must support PBX deployments, AI voice agents, and CRM-driven calling without compromising reliability, security, or compliance. For MSPs and resellers, operational infrastructure like usage rating, telecom tax automation, and clean billing can matter just as much as call quality.
If you are developer-first, platforms like Twilio or Telnyx may align with your architecture. If you are monetizing voice at scale and need a trunk plus a business engine behind it, a provider like Viirtue can reduce operational drag and protect margin.
The best choice is the one that not only connects calls today, but supports how you plan to package, sell, and scale voice tomorrow.
If you are interested in becoming a Viirtue Partner, click here to schedule your introductory call.
FAQ: Choosing the Best SIP Trunk Providers
What is the best SIP trunk provider for MSPs?
If you are reselling voice, the best provider is usually the one that combines carrier-grade SIP with the operations required to sell and bill it cleanly (usage rating, taxes, provisioning workflows). Viirtue is positioned specifically around this MSP and reseller model. (Viirtue)
Can I use SIP trunks to enable PSTN calling for AI agents?
Yes. AI agent platforms like ElevenLabs support SIP trunking so you can route calls between your telephony infrastructure and AI agents and support inbound and outbound calling. (ElevenLabs)
Why does STIR/SHAKEN matter when choosing a SIP trunk provider?
Caller ID authentication impacts deliverability and trust. The FCC describes STIR/SHAKEN as an industry-standard caller ID authentication framework and ties provider obligations to certification and mitigation programs. (Federal Communications Commission)
How many SIP channels do I need?
Size channels based on peak concurrent calls, not total users. If you are adding AI agents, plan for higher concurrency because agents can scale faster than human staffing.
