Adding/Removing Users in Categories

Is there a way for the admin to add/remove users from a category?  If a user accidentally subscribes to the wrong catagory.. Can I as admin remove that user from just that one catagory and not the whole system. 

For example:  I am trying to use this to send emails to various teams on my roller derby league.. and also to send to fans & sponsors that sign up on our website.  If a fan or sponsor sign up for the internal newsletter, is there a way for me to remove them from that without removing their whole subscription? Better yet, is there a way for me to block these catagories from the public and I can just manually input our rollergirls and staff for internal newsletters...  I tried testing it and when I remove a user from a category, it removes them from the whole system.  I do not see a link to add users to categories manually besides doing this when you import them.. However.. you cannot update this.. so if you add another category.. you will have to delete all users you want in this new category then import them again to add them back with the new category subscription.

I hope that makes some sense.  Is this a feature on the Premium edition? (I don't mind upgrading if it is).. If it is not a feature now.. Do you think it will be available in future releases?  I think this feature would greatly improve your product.

Thanks
Sumati
www.capitalcityrollerderby.com