The change/cancellation fee is $100 plus difference in fare if you were trying to rebook. Sounds like you had a highly discounted fare and the fees are more than the cost of the ticket. At that point you are better off just not showing up for the flight. Don't expect a refund or even a credi the fare purchased is less than the change fee so you'd be better off buying new tickets if you still want to travel, if not, just don't show.