Yes, 通話アプリ is free to download, however it contains in-app purchases or subscription offerings.
Not enough reviews to make a reliable assessment. The app needs more user feedback.
通話アプリ has several in-app purchases/subscriptions, the average in-app price is $861.67.
To get estimated revenue of 通話アプリ app and other AppStore insights you can sign up to AppTail Mobile Analytics Platform.