So I've read the Wiki and thought I understood it: it is possible to upgrade a ticket even if the reservation was made by a travel agency. I'm looking at a single segment that I'd like to upgrade using Avios from J to F. It's a BA ticket, issued on BA stock, and the flight is operated by BA with a BA code. I haven't started flying this itinerary yet.

And yet, MMB tells me that it is impossible to upgrade this segment online; and two calls to the BAEC call center yielded the same answer: talk to your travel agent. What am I doing wrong? Will my travel agent even be able to upgrade it on my behalf?

Shuly