I don't fully understand about SIM cards in other countries but my mobile company here told me this abt using my mobile in Singapore...
"Global Roaming charges are dependent on overseas networks and may vary without notice and also include an administration fee. In general Global Roaming charges are higher than if you were using the local SIM from the overseas country in which you’re using the service."
My question should I get a SIM card in Singapore, a local one? Can I do this? How do I pay for calls as I am billed monthly here. How much do they cost?