Virtual phone numbers for AI voice agents

Why a real virtual phone number matters for AI voice agents

Most AI voice agent demos run on the platform's built-in sandbox phone number — great for showing the agent works, terrible for production. Once you point real customers at it, the problems start:

• Answer rates collapse. Sandbox numbers usually carry STIR/SHAKEN B or C attestation, meaning US mobile carriers flag them as "Spam Likely." Answer rates drop 50-70%.
• International coverage breaks. Most sandbox trunks are US-only; outbound to UK / Germany / France / Israel either fails or routes via expensive transit.
• Latency adds up. The sandbox carrier's PoPs are often far from your agent's compute region. Each cross-region hop adds 30-100ms to turn latency — humans notice over ~600ms total.
• Margins disappear. Sandbox per-minute rates are typically 2-3× wholesale. At low volume it's fine; at scale it eats your unit economics.
• Number lock-in. Most sandboxes won't let you port the number out when you outgrow the platform — you have to start over with a new number and lose any brand equity.

The fix is BYOC — Bring Your Own Carrier — where you provision a real virtual phone number from a dedicated telecom carrier (like DIDHub) and connect it to your AI agent platform via standard SIP. You keep the number across platform changes, get carrier-grade signing, true wholesale pricing, and global routing.

How BYOC works with DIDHub

1. Pick a virtual phone number in DIDHub. Any of 130+ countries. Geographic, mobile, or toll-free.
2. Provision a SIP trunk. Dashboard → SIP Trunks → New trunk. Choose IP ACL (lock to your bridge's IP) or SIP digest auth (username + password).
3. Wire the trunk into your AI platform. Each platform has its own config form — paste DIDHub's SIP server hostname, port, credentials.
4. Route the DID to the trunk. Dashboard → Numbers → pick the DID → Routing → SIP Trunk.
5. Place a test call. Dial the number from any phone — the AI agent answers within ~1 second.

Total setup time: typically 5-15 minutes per platform.

Supported AI voice agent platforms

Don't see your platform? Any SIP-speaking agent works with DIDHub — the trunk is plain RFC 3261 SIP, no proprietary extensions required. Email sales@didhub.io and we'll write the integration guide.

STIR/SHAKEN — the difference between answered and ignored

If your AI voice agent makes outbound calls in the US, STIR/SHAKEN attestation is the single biggest variable in answer rate. Recap:

• A-attestation: originating carrier verified the customer is authorised to use the calling number. Calls show "Verified Caller" on iPhone, no spam label.
• B-attestation: customer verified, number not verified by carrier. Aggressively flagged as "Spam Likely" by T-Mobile, AT&T, Verizon analytics.
• C-attestation: carrier passing through — no end-customer relationship. Almost always flagged.

DIDHub signs all originating calls A. No configuration needed; it's the default. This is the single biggest reason AI voice agents see 60%+ answer rates on DIDHub trunks vs. 30-40% on most sandbox numbers.

STIR/SHAKEN deep dive · Attestation levels A/B/C explained.

Latency — sub-second turn-taking

Voice agent UX hinges on turn latency: the time from when the user stops speaking to when the agent starts responding. Below ~600ms feels natural; above ~1s feels broken.

The PSTN-side leg of that latency is dominated by SIP round-trips between the agent's compute region and the carrier's PoP. DIDHub operates regional ingress in 8 zones (US East/West, EU, MENA, India, APAC, ANZAC, LATAM, Africa) plus 200+ global edge via Cloudflare anycast — sub-50ms from any major cloud region in any major market.

Real-world impact: an AI agent running in AWS us-east-1 talking to a US customer over a DIDHub US-East SIP trunk has <30ms PSTN-side latency. Add ~200-400ms for STT + LLM + TTS = ~250-450ms total turn latency, which feels natural.

Pricing

Virtual phone numbers for AI voice agents are priced identically to standard DIDHub numbers — from $0.50/month in the cheapest markets (UK geographic) up to $5-15/month for regulated markets. No "AI surcharge."

Per-minute outbound (the main cost driver for an AI agent) starts at $0.005/min to US landline, $0.012/min to US mobile, and is typically the cheapest in the market because DIDHub aggregates supply across 8 wholesale carriers.

Inbound voice on geographic numbers is free; on toll-free numbers it's charged per-minute (you pay because the caller doesn't). See the live calling rates table for per-country specifics.

FAQ

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