I've found their "escalate" to be useless. They never called me back - three times I was given that line. I recently booked a mixed cabin booking. It took several chats and phone calls. Ultimately the thing that worked was to quote a line on their award chart that specifically said that this was their policy. Even armed with that it took another couple chats and a phone call. Seems to help calling during SIN biz hours - seemed somewhat more knowledgeable.

Bottom line: be persistent