curl --request GET \
  --url https://app.sendmux.ai/api/v1/billing/transactions \
  --header 'Authorization: Bearer <token>'

{
  "ok": true,
  "data": [
    {
      "id": "tx_clxxxxxxxxxxxxxxxxxxxxxxxxx",
      "amount": "-0.001500",
      "type": "PURCHASE",
      "description": "<string>",
      "quantity": 123,
      "balance_before": "<string>",
      "balance_after": "<string>",
      "created_at": "<string>"
    }
  ],
  "pagination": {
    "has_more": true,
    "next_cursor": "<string>"
  },
  "meta": {
    "request_id": "<string>"
  }
}