+1(514) 937-9445 or Toll-free (Canada & US) +1 (888) 947-9445
I only know of one guy ,who FAXED and e-mailed CHC isl for withdrawing his application and he got back his file in 7-8 days.
this is his ID.
http://www.canadavisa.com/canada-immigration-discussion-board/profiles/cheif-u208297.html