Hello,
As seen in the following article you are still billed when the Azure VM is turned off:
While the VM is shut down, there is still a storage cost for the disk that is holding the virtual hard drive file, as well as any other data storage disks you may have created, as you are still consuming file storage.
This resource group contains a VM that was shut down for the month of May and incurred a USD$0.31 daily cost for a 127GiB Premium SSD disk with locally redundant storage including a less than USD$0.01 charge for the storage account.
If you require more information, I would recommend you reach out to Azure Billing Support:
https://azure.microsoft.com/en-us/support/create-ticket
If this is helpful please accept answer.