AJ
That's right. SIA cargo would have bonded you and collected SGD35000, or SGD55000 from you as bank guarantee.
Your legal English contract with SIA cargo expires once you have completed your conversion training after 6 months. You will be transferred to GWA, where you will now be thrown with an actual legal Chinese contract, with reduced terms & conditions that were originally promised and advertised.
You can't really do much at this stage, after having committed yourself for six-eight months to Greatwall. You can leave, if you are willing to lose your SGD35000, or SGD55000. Signing the Chinese contract, will also lead you into a 1.9 million RMB debt if you decide to leave later.
Genghis