Purchasing Windows Server CALs you can contact volume license center support or windows server retail store support.
https://www.microsoft.com/en-us/windows-server/pricing
Also we have one Windows Server OEM 2019 license and 5 CAL license purchased in Singapore. Can I use the same on Azure Virtual Machine ?
This license allows you to install only one instance of the software for use on one device, whether that device is physical or virtual. If you want to use the software on more than one virtual device, you must obtain a separate license for each instance."
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