curl --request PATCH \
  --url https://api.retellai.com/v2/update-live-call/{call_id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "fields_to_override": {
    "override_dynamic_variables": {
      "additional_discount": "15%"
    }
  },
  "call_control": {
    "additional_context": "Customer just opened a support ticket about billing.",
    "trigger_response": true
  }
}
'

{
  "success": true
}