Unfortunately, you are most likely in the wrong: as a general matter, if you sign up for a service, then you have contractually obligated yourself to pay for it, even if you end up not making use of it. If the agreement under which you signed up for the class allowed you to cancel and avoid paying some or all of the $1,700, AND you cancelled in accordance with the terms of the agreement, then you should only have to pay that portion (if any) required by the cancellation policy. But without a policy in the agreement allowing you to cancel, you would be liable for the full amount.