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Voice call transfer

When a voice AI Agent hands a call to a human agent or to your phone system, the call is transferred with one of two transfer methods: a Standard transfer or a SIP REFER. You pick the method on the Handover action; this page explains how each one works, how they differ, and when to use which.

New to SIP?​

A few terms used on this page, in plain language:

  • SIP — the signaling protocol that sets up, changes, and ends voice calls. It carries the call control messages; the audio itself flows separately.
  • SIP INVITE — the message that starts a call to a destination.
  • SIP REFER — a SIP message that asks the other party to transfer the call to a third destination on its own, so the original party can leave.
  • SIP URI — a SIP address, like sip:agent@example.com (the SIP equivalent of a phone number).
  • PBX / phone system — the system on your side that receives the transferred call (for example a contact center or office phone system).
  • Bridge — keeping both call legs connected through Moveo, so Moveo stays in the call.

Standard transfer​

Moveo dials the destination and bridges the two calls: the caller and the destination are connected through Moveo, which stays on the call for its full duration.

It works with a phone number (E.164) or a SIP destination. Because both legs stay open through Moveo, recording continues through the transfer and both legs are billed while connected.

SIP REFER​

Moveo asks the provider to hand the call directly to your destination, then drops off the call entirely. Moveo is no longer in the path; the caller talks to your system directly.

It requires a SIP destination (a sip: URI), and the incoming call must have arrived over SIP — a caller who reached you over a phone line can't be transferred this way (use a Standard transfer instead). Once Moveo drops off, its recording stops at the handoff (recording continues on your side).

Which one to use​

Standard transferSIP REFER
Moveo stays in the callYesNo (drops off)
Moveo-side recording after transferContinuesStops at handoff
Destination typePhone number or SIPSIP only
Incoming call must be over SIPNoYes
If the transfer failsCall dropsCall drops

Use SIP REFER when the destination is a SIP system (a PBX or contact center) reached by an inbound SIP call and you want Moveo fully out of the path after the handoff — no second billed leg, and no Moveo-side recording of the agent conversation. Use a Standard transfer for phone destinations, or whenever the incoming call did not arrive over SIP.

Provider notes​

Twilio​

SIP REFER is only supported on SIP call legs. A call that reaches Moveo over a phone (PSTN) number or a browser (web) call cannot be transferred with SIP REFER; use a Standard transfer for those. See Twilio's <Refer> documentation.

See also​

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