iPhone Airplane Mode can not only be used for flights, but also be used in various situations. Read this post to get informed of when and how to use Airplane Mode on iPhone.
There are apps that allow you to make free calls on your iPhone. Here we summarize the top 5 iPhone apps for free calls. Just pick one and enjoy chatting with your friends free of charge.
You can use your iPhone as an ebook reader by using the iBook app. This article tells you how to transfer PDF files to iPhone by using iBook app and iOS Manager, so that you can read a variety of PDFs on iPhone.