The following is applicable for the solution.
Single SoR: Microsoft
Billing - Each SoR has its own billing portal, in this case the Azure Portal.
Payment:
Purchase directly from Microsoft get the same pay-as-you-go pricing through the Azure website or through an Azure sales specialist
Azure Partner for a managed cloud solution work with a partner for complete, managed cloud solutions for Azure
Cloud solution provider (CSP) partners will gain access to Azure services at pay-as-you-go rates for customers under the Microsoft Customer Agreement
Enterprise Agreement | Microsoft Volume Licensing is tiered to the number of computers or users being licensed
