The upgrade is processed in March, and I now hold a confirmed round-trip upgrade business ticket. The mileage upgrade is sponsored by my family member. However, due to the changing travel plan, I have to come back States one week earlier (7/22) than the original traveling date (7/29).

What is the whole process of rebooking upgrade flight? (Through checking online redemption system, upgrade is available.)

Should I just contact CX's USA reservation center to reissue my revenue ticket and rebook my upgrade? Or,

Should I need to ask my family member contacting MPC to change the upgrade?

Any comments/suggestions will be welcomed and appreciated.