Watson Assistant Integration with Phone Using Twilio

Hello I am using Watson assistant for voice(using Twilio SIP) I want to forward call to another number when user want's to connect to an agent or it's because of the flow. I am using the below method as mentioned in (https://cloud.ibm.com/docs/assistant?topic=assistant-dialog-voice-actions#dialog-voice-actions-transfer). But the call isn't transferring it just end's. and over here is some information too (https://cloud.ibm.com/docs/assistant?topic=assistant-deploy-phone#deploy-phone-transfer-service)

{
  "output": {
    "generic": [
      {
        "response_type": "connect_to_agent",
        "transfer_info": {
          "target": {
            "service_desk": {
              "sip": {
                "uri": "tel:+18883334444",
                "transfer_headers": [
                  {
                    "name": "Name",
                    "value": "Aymal"
                  },
                  {
                    "name": "Phone_Number",
                    "value": "4693061410"
                  }
                ],
                "transfer_headers_send_method": "refer_to_header"
              }
            }
          }
        },
        "agent_available": {
          "message": "I'll transfer you to an agent"
        },
        "agent_unavailable": {
          "message": "Sorry, I could not find an agent."
        },
        "message_to_human_agent": "New Patient"
      }
    ]
  }
}

{
  "output": {
    "generic": [
      {
        "response_type": "connect_to_agent",
        "transfer_info": {
          "target": {
            "service_desk": {
              "sip": {
                "uri": "tel:+18883334444",
                "transfer_headers": [
                  {
                    "name": "Customer-Header1",
                    "value": "Some-Custom-Info"
                  },
                  {
                    "name": "User-to-User",
                    "value": "XXXXXX"
                  }
                ],
                "transfer_headers_send_method": "refer_to_header"
              }
            }
          }
        },
        "agent_available": {
          "message": "I'll transfer you to an agent"
        },
        "agent_unavailable": {
          "message": "Sorry, I could not find an agent."
        },
        "message_to_human_agent": "The caller Wants to connect to human agent"
      }
    ]
  },
  "context": {}
}