curl --request GET \
  --url https://api.puretalk.ai/api/campaigns/{campaign_id}/leads \
  --header 'X-API-KEY: <api-key>'

{
  "count": 100,
  "next": "https://api.puretalk.ai/api/campaigns/123e4567-e89b-12d3-a456-426614174000/leads?page=2",
  "previous": "https://api.puretalk.ai/api/campaigns/123e4567-e89b-12d3-a456-426614174000/leads?page=1",
  "results": [
    {
      "to_number": "+1234567890",
      "is_completed": false,
      "variables": [
        {
          "var_name": "name",
          "var_value": "John Doe"
        }
      ],
      "call_id": "<string>",
      "completed_at": "2021-01-01"
    }
  ]
}