Calling AS is a waste of time - it sounds like the ticket is correctly issued, but SQ doesn't have the ticket attached to each segment of the reservation correctly. That can only be fixed on the SQ side.

If you have a lot of risk tolerance, you could also try flying the ticket without a reservation - if the flight fills, you'll be bumped, but if there are empty seats, SQ at the airport should be able to lift your ticket coupon and board you. I've done it with CA a few times - a bit stressful, but I've been lucky and it's always worked out