This chat is discreet, secure with a password to access messages and all messages are encrypted in the database.
You can add a contact with the number provided at the first connection, in the "Parameters" tab.
No need for a mobile operator, just a WI FI connection.

To choose your pass set:
By default the password are the first 3 horizontal dots.
So you can change your password in the settings.

Other option:
In the settings choose "Forgotten password".
A code will be sent to you by email, copy it and then go to the settings and choose "Change password" and paste the code sent to your Gmail box (watch the spam emails just in case).