Delete Azure AD with PowerBI Free

How to delete an Azure AD with Power BI Free license?

I can't delete it because of the Power BI Free license. 

Here is the similar post:

http://community.powerbi.com/t5/Service/Remove-Power-BI-free-from-Tenancy/m-p/298977/highlight/false#M34857

I also has an support ticket opened a couple days ago but no response yet.

Thanks,