Just spend an outrageous 35 minutes making a simple YYZ-YUL seat sale booking with the EP desk. Phone was picked up after 5 min wait then the agent put me on hold for a good 20 minutes when I asked for an upgrade using old stickers (probably asking for instructions on how to do it). However I do understand that they are new to AC system and it's better for them to find out how to do it than for them to tell you can't do it. It was tough for me picking CP operated flight in order to upgrade but enjoy it while it lasts! and best of all the upgrade was booked in C class!