As based in HKG now so working with CX is quite pleasant so far. Though most of the general hotline agents don't seem experienced enough to handle such complex ticket/changes. So you need to expect them to call back by their "back office" team within 48hours after they verify your itinerary and quote properly.
It's a similar experience when you make changes, even a simple one. I have made a simple change to rebook myself from a QR code flight to an AY codeshare(booked on the same QR flight but with an AY code yielding more Avios). The general hotline staff was unable to re-ticket it straightaway, so the case was sent back to the back office team to process.

In short, hotline staffs are nice to work with and fairly helpful and do have some idea what is a RTW ticket about but most of them don't have sufficient knowledge/access right to manually work with this type of ticket when system fail to do auto-price so chance for last minute changes are slim as you need to leave some lead time for them to process it.