I called to cancel a return PVG-YWG on a P fare.
Was told that I had to use the credit to fly Asia-Canada within a few months. Otherwise the fare would be re-calculated given that I booked a return ticket.

Overall makes no sense to me, but I just assumed that it's a weekend in Canada so hard to find knowledgeable staff.
Can anyone confirm? Thought I could apply the fare of the return as credit to a new ticket but that's not what it seems like.