Introducing the API for Elastic SIP Trunking Call Transfer (SIP Refer) feature. This feature enables you to move an active call from one endpoint to another. Twilio's Elastic SIP Trunking product supports "blind" call transfers. This allows you to configure SIP Refer on a Trunk using the API.
For details, please check our Elastic SIP Trunking API for Call Transfer via SIP REFER documentation.
As a side note, you can also configure Elastic SIP Trunking Call Transfer (SIP Refer) feature through Twilio console. Details of console configuration can be found here.