+1(514) 937-9445 or Toll-free (Canada & US) +1 (888) 947-9445
This letter is known as " Intention to Reside in Ontario" or Letter of Intend to reside in Ontario.
 
http://www.canadavisa.com/canada-immigration-discussion-board/invite-to-file-oinp-in-feb-2016-t396357.15.html

Check the sample letter in the above thread.