I am going through the deletion steps and after 72 hours, I will be able to update whether I can successfully delete the free Azure Active Directory to fully delete the Teams free org … it's obviously been a long time since your comment and I did struggle a bit to try to get through each step on the support page (couple hours at it) being a novice in Azure, but I think things are looking to be on the right track for finalizing the deletion of org/MS Teams free in a few more days (depends when I remember to check it/try it again)
@TAL_GER the support page link from the OP includes step 2. which indicates how to find the admin ID to use to reset password and login to MS365 ... you also have to be the person assigned as the global admin role to delete all the team/group members and be the only one left in the group/team/org before moving on with the remaining steps. There is a visual example and though now that I've gone through past that, I can't remember if the "ID" beside the Role column was the same admin email address that I needed to use for next steps (I signed out of Teams after I finished deleting all other members). For me, the admin email worked to reset password through security code sent to alternate email (the original one used to sign up for Teams Free, in my case a personal Microsoft email address).
This is the support link I followed and am now in the 72hr window for final deletion of free/trial subscription of MS Teams before I can proceed to delete the directory in Azure Active Directory :
Successfully deleted the Teams free org/azure directory.
Hope anyone else that tries will succeed following the steps and the trickiest part for me was understanding how to clear the 'errors' related to deprovisioning any/all licenses or subscriptions (following those steps worked, but I found it tricky and confusing to do).
I was able to delete active directory for an unneeded org/Teams free. Did you get stuck on trying to cancel/delete licenses or subscriptions like me, or, are you roadblocked somewhere else in the how-to steps?