I think I actually used one of the "past travel" links here:

http://www.aircanada.com/en/customercare/index.html

I had a similar problem, and have heard this from others many times, that when re-booking the agents typically just put you in the lowest available fare class regardless of what you booked. Mine was a bit of insult to injury since it happened in combination with a missed connection/forced overnight in YUL due to a "communication error". The plane went to the wrong gate on the wrong side of the terminal and getting stuck there for a while. With the tight connection due to an already late departure I was going home that night.