When a smartphone had a telephone, this application covers a registration name with a phone number and the telephone book. When it does not want to be known by a person whom you had a telephone from, it is convenient.
There is not the close function, but it is available and does it in the specifications that controlled battery consumption by simple operation.

(attention)
The smartphone of Android is released by many makers and cannot guarantee the movement with all models. I hope that I have you use it after having confirmed that I work without a problem. When you do not work normally, I cancel the use, and, please uninstall this application.