We had an SCL - YYZ flight booked for 2 pax on a Wednesday morning in July 2019. These are I class tickets on 016 stock, booked using UA MP. Due to a recent schedule change, that flight now operates on Tue and Thu evenings, but not Wed. The system automatically moved us to Thu, but we'd rather have it moved to Tue. I called UA and asked to change, but they said no availability, too bad. Asked them to contact AC and ask for change, but they would not. Can AC do anything or am I out of luck here?