@Handian Sudianto Welcome to Microsoft Q&A Forum, Thanks for posting here!!
You can verify the usage of the Storage account by checking the transactions from Metrics, if there is any egress or ingress activity during the last 30 days.
You can filter on Metric Namespace File, Blob, Table and Queues. And the metrics Ingress or Egress.
For example: In the screenshot you can see there is no activity since 5th of December
Hope this helps!
Kindly let us know if the above helps or you need further assistance on this issue
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