I’ve searched for this and the only answer i’ve found is “contact our support”:
As a Company Admin i should have this option.
We (and probably many other companies) manage our licenses according to our own request/approval process.
If anyone can upgrade to a full license without our knowledge, we have to monitor it more often and it causes us unnecessary work.
A second Problem is, that although we registered our domain and manage it, we can’t stop users from registering themselves.
So my wish list points are:
-give Company Admins the option to set the “free-restricted”-license as default for new users
and/or
-give Company Admins the option to block users from registering themselves in our managed domain
