curl --request GET \
  --url https://your-instance.example.com/api/calls/statistics \
  --header 'Authorization: Bearer <token>'

{
  "success": true,
  "statistics": {
    "totalCalls": 124,
    "totalDuration": 18450,
    "averageDuration": 148.79,
    "byStatus": {
      "completed": {
        "count": 102,
        "totalDuration": 17800,
        "avgDuration": 174.5
      },
      "no-answer": {
        "count": 18,
        "totalDuration": 0,
        "avgDuration": 0
      },
      "failed": {
        "count": 4,
        "totalDuration": 650,
        "avgDuration": 162.5
      }
    }
  }
}