In Reply to: What if its another carrier? Same codes? posted by Baliforever on Monday, 17. December 2012 at 14:10 Bali Time:
To SMS from any carrier to an Australian number it is +61 and then the number with the first 0 removed.
To call from any carrier, you can use the same as above but will be charged the full international rate. The cheap call prefix is different for each carrier. Whoever sets up your SIM should give you that info.
I've never had to ask for it - they've always used a marker and written on the card that the SIM came in, the SMS and cheap call prefixes as well as the number you call to check how much credit you have left.