well say.I would suggest you get a $5 Senior Plan from the SIMBA Shops first with random number and cash payment (please don't pay extra, I know some ah Beng shop will try to say need pay $10 or something extra for "sim card" cost) and test the network. If it works for you, then sign up new line and port over.
If it doesn't, at least you won't be stuck and think of it as eating one less plate of chicken thigh rice.
Besides, they don't deduct call time when you call sg mobile number, except for land line. Further, they give you free 1 GB auto roaming to many countries, that is a bonus.

