Yes you can do that.
They charge you $50 if you cancel it less than 31 days before the scheduled date. Since, it's in early May and we are almost in the month of May, then you will be charged.
You will be charged even higher amount if it is less than 5 days of your scheduled date.
For more details read here http://www.usmle-forums.com/general-...cheduling.html