If you have Maxis mobile and you find that overseas/international calls are very expensive, why not try using their Internet phone facility? The sound quality is still as good.
To use their Internet calling facility, just dial 132 before you dial the phone number:
Dial [Country Code][Area code][Phone number]
 is optional
Check out their price here for the various countries
For calling Brunei from East Malaysia, it cost only 0.165 cents every 30 seconds.
Calling Singapore is just RM0.25 for every 30 seconds.