Phone numbers for Retell AI — SIP trunk setup with DIDHub

Why DIDHub for Retell AI

• A-attestation on US outbound. Retell's bundled DIDs are typically B-attestation. For sustained answer rates on T-Mobile, Verizon, and AT&T, A-attestation matters. DIDHub-allocated US numbers are signed A by default.
• 136-country coverage. Retell support international, but your inventory is the bottleneck. DIDHub provisions in 136 countries with per-country regulatory clarity (KYC, port timing, regulator) shown before you sign up.
• Predictable per-DID pricing. $1.99 US, ~$1.10 German, ~$0.63 UK London — no commit, no setup. For Retell deployments where you allocate per-customer DIDs, the math is straightforward.
• Webhook events match Retell's pattern. DIDHub fires call-started, answered, ended, recording-available, transcription-ready webhooks — signed payloads, retry-friendly. Same shape as Retell's own events for clean correlation.

BYOC setup — step by step

1. Sign up at /signup and provision the DID inventory you need.
2. Generate DIDHub SIP credentials in your dashboard.
3. In Retell AI: open Phone Numbers → SIP Trunk (or current equivalent path) and configure Bring Your Own Carrier.
4. Paste DIDHub's SIP URI and credentials into Retell's BYOC config.
5. Bind specific DIDs to specific Retell agents (Retell calls these “agents” or “assistants” depending on UI version).
6. Test inbound + outbound calls. Validate STIR/SHAKEN attestation on the receiving carrier.

Caller-ID configuration

Configure the DIDHub DID as the From-header in Retell's outbound calls. Retell passes the SIP From through DIDHub's edge; we validate and sign 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 Retell AI 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 Retell AI DID

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