Removed members' emails and accounts still accesible in Teams

Hello,

Here is the main problem:

how to completely remove members accounts from any MS service, and also from Teams.

I know how to do it via Azure AD, that's obvious.

However, accounts removed from there are available on Teams.

Restarting Teams does not help.

I can still chat with the account (visible per email) which is removed.

Or, the type of the same problem: I have added an account, then removed, supposedly completely, not seen in Azure. Then I cannot add it again on Teams. During 'Add' process red error message appears.

Eventually, we come to the first question: how to completely, from all temp files, resources (whatever) remove an account.

Any help would be highly appreciated.

Cheers,

Piotr