Sounds massively fishy unless OP deliberately worked with a travel agent (even then the add on charges seem bogus or at a minimum inflated).

For OP I'd suggest you call SQ (the real one, at +1-833-727-0118) in the US or Singapore (there are cheap ways to do that) and talk to them. Get the numbers from SQ website and don't rely on Google search results as the scammers pay for their numbers to show at the top.

Also you can look up your bookings on the SQ website under manage booking function using PNR reference and Name (plus paxes last name that are in same PNR) and there is no need to be a Krisflyer member. See what you see there with regards to unconfirmed seats and such.