Hi Rasik Dudhagra,
Thank you for reaching out to the Microsoft Q&A platform.
Based on the error message Change in disk property of VM of size 'Standard_A8m_v2' is not supported.
Standard_A8m_v2 is an old size, could you please provide us the below details:
What change you want to make.
What is the OS and region of the VM.
I would suggest you Resize the VM to a Larger Supported Size.
Please find the below document for your reference:
https://learn.microsoft.com/en-us/azure/virtual-machines/sizes/resize-vm?tabs=portal
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