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Voice-AI SIP trunking is available only on Fonial’s paid PLUS plan. On the FREE tier, ask Fonial support (0221 66966966, support@fonial.de) whether your account can be upgraded before starting this setup.
There is no dedicated Fonial import. Connect a Fonial number the same way as any other provider, through Numbers → Add SIP integration — but Fonial’s setup splits across two separate mechanisms rather than one shared trunk:
  • Outbound — a Fonial SIP user supplies the credentials the platform authenticates with.
  • Inbound — a Fonial destination (Ziel) forwarding to a SIP URI sends calls to the platform’s SIP address.
The Fonial SIP user stays Offline in Fonial’s dashboard permanently — that’s expected, not a fault. The platform never sends a SIP REGISTER; inbound calls arrive through the forwarding destination, not through registration.

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Set it up

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1. Create a SIP user in Fonial

In the Fonial customer portal (kundenkonto.fonial.de), open SIP-Benutzer and create a new SIP user (any name, e.g. Famulor). It appears in the list with status Offline — leave it that way.

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2. Open its credentials and assign the number

Open the new SIP user’s credentials to get its username, password, and server URL (sip.plusnet.de). Then, under Rufnummern, select the number to connect and assign it to that SIP user.

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3. Create the platform SIP trunk

In Numbers → Add SIP integration, use these settings: Copy Our SIP address shown under inbound settings (e.g. xxxxxx.eu.sip.livekit.cloud) — you need it next.

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4. Forward the number to the platform (inbound)

Build the SIP URI from the Fonial number without the leading + and the address copied in step 3:
Example: +498956546546 and xxxxxx.eu.sip.livekit.cloud become sip:498956546546@xxxxxx.eu.sip.livekit.cloud. In Fonial, go to Telefonanlage → Ziele → Neues Ziel anlegen, choose Weiterleitung (Mobilfunk, Festnetz, Fax oder SIP-URI) as the destination type, name it, select Weiterleitung auf SIP-URI, paste the SIP URI above, set the outgoing number to the Fonial number you’re connecting, and save.

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5. Assign an assistant and test

Assign the connected number to an assistant, then call it externally to confirm the assistant answers.

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Common issues

Expected — see the note above. The platform never registers; inbound calls use the SIP-URI forwarding from step 4, not registration.
Check the SIP-URI forwarding (step 4): correct number format (no +), the exact Our SIP address copied from the platform (no extra sip:, no whitespace), and the right outgoing number selected on the Fonial destination.
Recheck username, password, and sip.plusnet.de from the Fonial SIP-user credentials (step 2), and confirm the outbound calling number format is set to international with +.

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Validate the setup

Call the connected number from an external phone and confirm a new inbound record in History, the assigned assistant, and two-way audio. Then place one outbound test call to confirm the SIP-user credentials independently. Sources: Fonial trunking setup. Accessed 22 August 2026.