Hi @Leming Shen ,
to get an idea what happens it might be helpful to take a look in the Cost Analysis in the Azure Portal:
Quickstart: Start using Cost analysis
This way you can see the consumpotion, costs and details per resource filtered by date/timespan.
Another option might be to open a support case with Microsoft Azure support for clarification.
Azure Billing and Subscription support is offered by Microsoft by no cost and it's for free.
Source: Azure Support plans
(If the reply was helpful please don't forget to upvote and/or accept as answer, thank you)
Regards
Andreas Baumgarten