Read these tips to ensure that your phone doesn't incur data roaming charges while you're overseas.
5. Manage your smartphone
Stop your apps from receiving data updates or sending info over the 3G network.
Check your settings and disable the appropriate functions such as notifications or hourly updates so that these apps will not access mobile networks when you're overseas.
Make sure that your data roaming function is switched off at all times, even when you are in Singapore.
If you need to conserve battery power, you should switch off your 3G even when in Singapore and only switch it on when necessary - this is a sure way to make sure that 3G access is always within your control, whether you are in Singapore or overseas.