I think people use chat Apps like iMessage more than Email. Fortunately, Apple users have the excellent iMessage App to use on their iPhones. The iMessage App is designed for texting with people, but if you need to call the person you are texting, you can do so easily.
iMessage Text Call
A typical iMessage text looks something like this.
To call someone during a texting session, you have to do is tap on their name in the upper portion of the window. In the next screen, just tap on the icon for what you wish to do either a Voice call or FaceTime call.
The iPhone immediately brings up the appropriate App and makes the call.
I guess this is kind of a no-brainer, but it is nice to be reminded that you can do this. The fact is sometimes what you need to communicate is just too much information for a text. A call is much more efficient.