Thanks guys, so the 6 month limit seems to be the reason then. The ticket was booked through Ctrip and I was never provided with any terms and condition that talked about the 6 month limit (nor anything that talked about Change Fee for that matter).

This 6 month limit was never advertised at the time of booking. Had I known that, I would have definitely booked with another airline.

I contacted Ctrip today for this terms and condition that they said to contact Air Canada.

I contact Air Canada and they said to contact Ctrip.

In short, I never received, and still don't have the terms of carriage.

Is there anywhere I can complain to besides the Canadian Transportation Agency?