I just went through this on a couple of recent flights where I ordered a meal tray and upgraded beverage and much to my frustration was charged $10.00 for the privilege. Sent in a complaint via the online form and got some aeroplan points for my troubles (not that I really need more of them) and much to my surprise got an e-mail from their service provider telling me they are looking in to it.

Please do as I did and send in your complaint - the more people who bring this to their attention the more likely they are to actually try to solve it.