@calgia di you have onprem AD and sync it to Azure AD? If yes you can update the users details in local AD and sync across. Also check this page - https://support.microsoft.com/en-us/office/change-your-user-name-and-initials-cdd4b8ac-fbca-438d-a5b5-a99fb1c750e3
Hope this helps.
JS
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