It is possible to move a customer from one course to another with no additional charge. Please note that all absence/attendance records will be lost (and consequently the right to book catch-up classes in case of absence).
Just open the user's profile and click on the name of the course. A new window will open up, where you can find the button 
In case the course involves attendance more than once a week, the Change Course button will be visible only after clicking on the Detail button, as the person might require to be moved from one course but not necessarily from both. 
To proceed with the change of course, select the necessary filters and click on the yellow button. Then pick the new course and click on Change Course. The enrolment will start on the date specified in the filters. If no date is specified, the customer's enrolment on the new course will take place immediately.