Hi,
Initially you will have to transfer the Subscription from the Service Provider to Microsoft account - https://learn.microsoft.com/en-us/azure/cost-management-billing/manage/billing-subscription-transfer
Also you can contract Microsoft Billing Team for detailed information - https://learn.microsoft.com/en-us/azure/azure-portal/supportability/how-to-create-azure-support-request#go-to-help--support-from-the-global-header
Hope this helps.
JS
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