Every time a client

Every time a client books a session, I get double notifications (as I a both the admin and the service provider). This is getting annoying when a lot of clients are booking. I request an option to disable double notifications, for circumstances such as this one.
I've tried this snippet and no luck, i've tried disabling the setting in the image, but i dont get no confirmation at all, Thanks in advance

add_filter( 'app_get_admin_email', 'app_get_admin_email_cb' );
function app_get_admin_email_cb( $email ){
return 'example@example.com';
}