@Chuong Phung It would be very difficult to estimate why you have been charged more for the usage without looking up the usage reports of your resource. I would advise you to raise an azure support case under billing category to get details of the usage and billing to check further, raising a support case for billing related queries does not require a support subscription and the service team should get back to you with details of the breakup. Follow the steps here to create a support request with problem type billing. Thanks!!
You can also lookup your usage and estimate costs for the future using monitoring metrics of your resource. I hope this helps!!
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