Our crew hotac is the Royal Plaza on Scotts
25 Scott Road
The hotel does crew rates for us when staying in our own time and it is a very nice hotel. Overseas tel charges from SIN, even from your hotel phone, have to be amongst the cheapest and best value in the world so I wouldn't stress too much about that. Cards are readily available.
Its also very nicely located for shopping, night life etc.
If you want contact details for them (and a couple of good steers for bars etc) just send me a PM.