There are a couple ways you could do this in LMScheckout. If you go to the Purchases page in the Commerce tab in the admin area, you can find the original order and then cancel it from here. That will unenroll them from the current course but it will not refund the money unless you go into the merchant account and refund it from there. Assuming you want to keep the money and just move them to a new course, you could then create a new purchase on this page and just use the invoice option. This way it will not charge them again and it will generate a purchase for your records showing what course they should be in. If you don't need the purchase record, then you could also go directly to the course in the course settings area in LMScheckout, expand it by clicking the plus sign and then click on the course roster button. You can add a user this way and it doesn't generate a transaction record.