Originally posted by jeRrRKKK:
how to go about doing it? requires a fee?
Just go to any of your mobile service provider's outlets.
For me, it was SingTel and I changed mine at the Tampines Mall branch. There is a small fee (can't remember....between S$10 to 30)....but they didn't charge me for it because I told them that I've been getting prank calls, etc. Also, I've always paid on time (through many years).