Guide for Google Duo - simple video calling

Guide for Google Duo - simple video calling
I made this guide for my interests and share experiences with others.

My apps has some tips such as:
+ All you need is a phone number
+ Add or block numbers from calling you
+ Get great video and audio quality
+ Turn Knock Knock on or off
+ ...
If you have anyproblem about the application, please contact me at: [email protected]