Optus, like other Australian mobile carriers, traps users into excessive charges by giving delayed billing information and refusing to show on your mobile "remaining uasage" in dollars and cents, that would allow the user to stay within the cap and the budget. Their roaming data GPRS and overseas call charges are truly exhorbitant, i.e. I paid 4000 times the fee for using Internet on my mobile I would have paid had I used a local Thai sim card (which I eventually did). Never use your Optus mobile overseas for any purpose unless you are... read full review »