In Reply to: Mobile Phone Coverage posted by lx_mello_xl on Friday, 7. January 2005 at 15:17 Bali Time:
Bali Sim will only work in your phone if it is not locked to the Optus network.
You can check by ringing Optus, see what was on the box when you bought it or try a sim card from another network to see if it works.
I just had one our Telstra ones unlocked today.
Also scroll down the page for other posts asking same/similar questions & search the archives as there is heaps of info on this & mobile phone topics in general.