You can download your invoice in the Azure portal or get it sent in email. Invoices are sent to the person set to receive invoices for the enrollment.
Please checkout these docs for the steps:
View and download your Microsoft Azure invoice
Download or view your Azure billing invoice
You may always file a (free) support ticket with our Azure billing/subscription support team: create an Azure support request. Select Subscription Management for the issue type.
Checkout this FAQ: How do I submit a support request if I can't sign in to the Azure portal?
Call the customer service number for your country/region. https://support.microsoft.com/topic/global-customer-service-phone-numbers-c0389ade-5640-e588-8b0e-28de8afeb3f2
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