I'm from the U.S.A. visiting friends in Canada and I'm not sure when my visitor's visa is intended to expire. I've been told that the expiration would be stamped on my passport, but the only stamp or date inside of it is my arrival date. I have searched online for phone numbers to call and ask them personally, but I have been unable to garner helpful information. Who am I supposed to contact so I know for sure the date in which I need to leave?