FlyerTalk Evangelist
Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: BA Silver, TK E+, AA PP, Hyatt Globalist, Marriott LT Plat, Hilton Diamond
Posts: 13,046
Try HUACA.
However I can see how VS might not be able to change a ticket issued by a travel agent, in order to add a companion. And I don't quite see how a companion ticket could be issued on its own, since you could then go and cancel the originally-booked ticket (leaving the cheaper "companion" ticket in place). But I'm just speculating...