This is not about Office 365. we just use the Office 365 commerce portal as a landing point. You can use it even if you are not an Office 365 customer. You just use your Azure Active Directory global admin credentials to login and follow the process.
Plz try it and let us know if it worked for you.
Of course plz keep in mind that for managing Azure services you probably don't need Azure Active Directory Premium. The free version is just fine.
Azure Active Directory Product Manager