When the original caller is transferred from one extension to another extension(or to any other number), I couldn't find a reliable way to identify, from whom to whom the call was transferred.
From the call log API(/restapi/v1.0/account/~/call-log?&view=Detailed) , Only info related to call transfer is in call leg as given below:
{
"action": "Transfer",
"direction": "Outbound",
"duration": 21,
"extension": {
"id": 249697004,
"uri": "https://platform.devtest.ringcentral.com/restapi/v1.0/account/249331004/extension/249697004"
},
"from": {
"extensionId": "249697004",
"name": "Nanda Kumar"
},
"legType": "TransferCall",
"result": "Call connected",
"startTime": "2019-07-18T08:46:36.185Z",
"to": {
"location": "Los Angeles , CA"
},
"transport": "PSTN",
"type": "Voice"
}
Which does not have the proper `to` and `from` values.