Originally Posted by
marcuslai
.....(a) presumably i wouldn't need to find dates where both H and U are available ?
(b) and i would go about this change simply by talking to CX MPC, and would not need to involve the travel agent who booked the economy tickets ?
Unfortunately, you do need to find dates with both H and U availabilities.

Some CX MPC agents will handle both for you, some will ask you to call your TA to change the H booking first (or creat a new H booking). It depends on who you get.