Hi @Abdullah Miah ,
Hope you are doing well,
We can update the users phone number using below Graph PS SDK with this Command .
Update-MgUser -UserID "Emailadress" -mobilephone "10101010101"
Please refer this link for More details
-https://learn.microsoft.com/en-us/powershell/module/microsoft.graph.users/update-mguser?view=graph-powershell-1.0
Currently , we can update only the listed properties of user by using graph API endpoint. and currently there is no property to update the Phone number type using graph.
For Additional reference follow this link
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