Hi @KA SAN CHAN ,
Billing records are generated and uploaded to Azure twice per day, and the charges only start based on the configuration after the 60-day trial is over. If the configuration changes, this would be reflected in the billing records accordingly. If you are only evaluating HCI for testing, it would be best to opt your servers into the preview channel. This will allow you to continue using HCI without worrying about billing, however, know that this is ONLY for testing purposes. You cannot use preview builds in ANY production scenario (this is also true for running HCI in virtualized environments - testing only). Also, once you have opted into the preview channel, you are not able to opt out without reloading.
More information on the preview channel can be found here - https://learn.microsoft.com/en-us/azure-stack/hci/manage/preview-channel
Hope this helps!
Trent