Singtel has launched a multi sim card function not long ago. Many users though they can combine different numbers to be use on one sim card but this is not the fact. You can only use one mobile number only but it allowed you to use it on different handsets, blackberry and laptop at the same time.
The definition of the Multi Sim card is as follows:
Multi-SIM service enables you to
have just one mobile line and multiple SIM cards (up to max. 4 SIM
cards). Now you can enjoy the convenience of using one mobile number
across multiple handsets or devices to make simultaneous data transfers
while talking on the phone.
You will be issued multi sim cards up to a max of 4 sim cards. At any one time, all Multi-SIM
cards can make outgoing voice calls/video calls/SMS/MMS. Only 1 of the
Multi-SIM card (term as Preferred Card) will be able to receive voice
calls/video calls/SMS/MMS. ALL the Multi-SIM cards@ will be able to use
data simultaneously. So, you can make a voice call while working /
surfing using a PDA/laptop/Blackberry.