Flying from YYZ to YYC in Business (paid). Can someone please advise me whether I can request same day change from AC 159 (dep 2100pm B738max) to AC 157 (dep 1955pm on B787) on Dec 18? I will have check bags. Do I just check in early and make the request at the check in desk? I have *G status if that matters, not AC *G though. Many thanks!