Well, that wasn't the end of the story.
While in Europe I received an email with a new itinerary from WY, changing MXP-MCT to LHR-MCT, as I had previously suggested via Facebook message, and which was completely ignored by the call centre.
Even though it was very late in arriving, it seems to show that bypassing the call centre, if at all possible, is the way to go.
The WY call centre seems very similar to the QR call centre IME (ie quite hopeless). I wonder if it is the same one?