OK, it looks like I have done something wrong with my customer self-registration. Currently, when customers self-register for our portal, it also registers them in my "users" section. Of course, after they register, they get an error stating "there are no more licenses available". I need a good detailed tutorial on setting up self-registration that ONLY adds them to the portal and nothing else.
Side note... I do not want open registration to external customers, only internal customers using our domain email.