How to find out which email address from our domain has registered our domain as organsiation

[MS-Teams-User]

At the moment we are not able to register our organisation in teams because this is alrady done. But how to find out which email-adress has done this?

This email-address is the administrator of our teams domain, but currently unknown.

[#2]

Hi!
Please read through this:

https://docs.microsoft.com/en-us/azure/active-directory/enterprise-users/domains-admin-takeover

Adam