Phone numbers for Vapi — SIP trunk setup with DIDHub

Why DIDHub for Vapi

• STIR/SHAKEN A-attestation by default. DIDHub-allocated US/CA numbers are signed with attestation A on every outbound call. Vapi's bundled DIDs are typically B-attestation, which mobile carriers increasingly flag as “Spam Likely.” Bring your own DIDHub trunk and the spam labeling problem goes away on day one.
• 136-country DID inventory. Vapi's bundled US numbers are great for US-only deployments. For multi-country campaigns — UK, Germany, Brazil, Israel, UAE, Singapore — bring DIDHub DIDs via BYOC.
• Per-DID flat pricing, no commit. $1.99 for a US number, ~$1.10 for German, ~$0.63 for UK London. No minimum order quantity, no monthly minimum, no setup fee on standard SKUs.
• Bulk DID provisioning API. POST one DID per onboarding, attach via Vapi's BYOC config. The Vapi assistant assignment can be metadata-driven so you bind DID ↔ agent in your application logic.
• Regional SIP/RTP edges. Sub-50ms ingress to your Vapi inference region. Lower latency = more natural conversation.

BYOC setup — step by step

1. Sign up at /signup and provision the DID(s) you need.
2. In the DIDHub dashboard, generate SIP credentials for your Vapi tenant (or get an IP-allowlist if your Vapi org runs from fixed IPs).
3. In Vapi: open the Phone Numbers section, choose BYO SIP Trunk (or equivalent label), and paste the DIDHub SIP URI (typically sip.didhub.io) plus authentication.
4. Create a Vapi assistant if you don't already have one. Assign the assistant to the BYOC phone number.
5. Test inbound: dial the DID from a mobile. The Vapi assistant should answer.
6. Test outbound: trigger Vapi to place a call from the DID. Verify Caller-ID, STIR/SHAKEN attestation, and audio quality.

Caller-ID configuration

Set the DIDHub-provisioned DID as the outbound Caller-ID in your Vapi assistant config. Vapi will pass that as the From-header on outbound SIP INVITEs; DIDHub validates the Caller-ID against your allocated/ported inventory and signs the call with A-attestation.

For US/CA outbound: DIDHub signs every call with STIR/SHAKEN attestation A on DIDHub-allocated and DIDHub-ported numbers. This is the level that mobile carriers (T-Mobile, Verizon, AT&T) treat with baseline trust — calls signed with weaker attestation are increasingly flagged as “Spam Likely” or sent straight to voicemail. See STIR/SHAKEN explained for the full background.

For non-US destinations: present a local DID as Caller-ID for best answer rates. AI agent calling a Madrid customer should present a +34 (Spanish) Caller-ID, not a US number. DIDHub serves 136 countries with dedicated landing pages so you can match Caller-ID to destination.

Latency & regional ingress

Realtime AI voice is brittle to network latency — an extra 100ms of SIP egress can break the natural-conversation feel. DIDHub operates SIP/RTP edges in:

• NOAM: Ashburn (US-East), San Jose (US-West), Dallas
• EU: Frankfurt, Amsterdam
• APAC: Singapore, Tokyo
• MENA: Dubai

Pick the edge nearest to your Vapi inference region. Typical sub-50ms regional ingress for the closest pair. If you need a region we don't list, talk to [email protected] — we add edges in response to customer demand.

FAQ

Provision your first Vapi DID

Sign up at /signup, pick a country / area code, and route the DID to your Vapi BYOC SIP trunk. $1.99/mo for a US number, sub-60-second activation on most countries. No commits.