best to call singtel ask them send technician over.
last time i called them, they kept sending phone technician, for
like 3-4 times they checked and found no problems.
it's only when they send those networking technician over that
they got the problem resolved, seems like my entire cable from
house to singnet was screwed, they changed it and i haven't had any
problem since.
You're one lucky guy I should say.
There were once I called singnet several times due to my brand
NEW mio router keeps getting disconnected. Guess what? Those
freaking guys refused to send someone down, insisting there is no
problem on their side. 
So
what about my side? 
So tinuviel07, good luck you will need it. 