We had an SCL - YYZ flight on AC metal booked through UA MP for 2 pax leaving on a Wed morning in July 2019. These are I class tickets. Due to a schedule change, that flight flight now operates on Tue and Thu evenings, but not Wed. The system automatically moved us to the Thu flight, but I'd like to depart on Tue instead. There's no I class available on the Tue, but can UA work with their AC liason to get this changed?