@edwinlin88 once everyone starts to use the free cross platform messenger it will be standard. WhatsApp does more than just SMS and it's a lot cheaper. Mobile Networks make a whole lot of money from SMS when all they're doing is sending a very small amount of data.
WhatsApp on the other hand will work when you're home from your wifi(free), when you are out it will use 3G/4G at a third of the cost (depending on your network).