OKTech & M2.6 - How to remove only one role (Teacher) in a course with multiple roles (Teacher,Student).

I can't seem to figure out how to remove a Teacher role from a user who has multiple roles in a course (Teacher and Student). I want to preserve any user data in the course, so I don't want to fully unenroll them and then enroll them again.

Any tips?  

I'm using the OK Tech plugin and Moodle v2.6.

Thanks