Membership

There are 3 levels of access to my site.
1. Visitors who can see certain blog posts.
2. Free basic level members who have access to all except the program groups 3. Free members who have access to all of the site (apart from admin)
I have set up access levels for all 3 categories. I added associated roles to the 2 member groups and assumed because of this that signed in members would automatically have access to at least the basic level. Instead I have to manually add the level of each member before they can view any of the members area. This means that when they activate their account and log in straight away they cannot get to the members area.
Am I doing something wrong or is this how it is meant to be?