Fee withdrawal policies vary from school to school. Usually it's refundable if you apply within 10 days of course start. There maybe some charges on it though. Better contact your school asap
I may be treading on personal territory but may I ask why after going through all the difficulties of securing study permit and then after coming to Canada you want to go back. I know it is a difficult transition but the end result are worth it believe me I am speaking from my own personal experience . Think twice many people don't get this chance.