I had a 10% off aeroplan code I used for a YYZ to LAX flight.

I have to change and go to Sydney now in the same time period. AC isn't offering the reasonbly priced United flight, so I'd rather go through YVR and try and use my SSWU.

I called, and reservations says I can cancel the flight and get a credit, then book a new flight, but not use the credit and the promo code together, because there's no way to use a promo code over the phone, and there's no way to use a credit over the web.

So, unless some clever person out there can tell me how to do what I want (interestingly by the way, YYZ - LAX - YVR - SYD is cheaper than YYZ - SYD via YVR) I'll just book on united and buy up on check in (I always get offered something by United not sure why). It's one of those times AC loses the revenue because they won't do what should be quite possible (which is kinda too bad I'd rather fly them than UA).