1)I message, Apple users only need to access the network directly, and there is no SMS fee. Moreover, wifi is very popular in the United States, and basically there are wifi signals in buildings. And if you are a user of Xfinity, you can also use their public ***wifi. 2)Whatsapp, it feels like the prototype of WeChat, and the interface is very similar. The function is more simplified. But it seems that young people use it more.