In that case I had misunderstood. The error is that the ICC didn't ticket the flights in time; SQ cancels reservations that are not ticketed within 24 hours. The seats have subsequently been booked by someone else. Therefore, you have some justification to expect BD to put themselves out to correct their error. Ask them, given that you have presumably already paid your cash and miles, to book you onto revenue seats. It's their fault and if they don't like paying for this sort of thing, then they need to spend more on proper booking agents. If and only if you get no joy with this, ask for an equivalent routing with Lufthansa (i.e. for them to open seats in C for you). The pre-travel support number can be found by searching, I expect. I don't know it or I'd post it.