Sorry to hear of the difficulty. You’re probably more likely to get some joy from the ICC if you offer a solution rather than a problem. For various reasons, it may be difficult for BD to get you flights in C with SQ. Legally, I think your position is weak if you have had more than two weeks notice of the cancellation. If it is shorter notice than this, then BD or SQ is obliged to find you an alternative and equivalent routing. But I’m not an expert on this and others will doubtless be able to give chapter and verse.

When I had a redemption torpedoed by the cancellation of a route, BD were able to open a LH flight for me. Are there flights available via FRA? Alternatively, are there routes through BKK or JNB that you might consider (although I know C availability on SA is awkward).