This app was mentioned in 1 comment, with an average of 2.00 upvotes
Didn't use the call feature but as for reliability -the app was down 3 of 6 days we tried to use it so it wasn't reliable for us. That was on the Breakaway, not sure if the app was shit or network/server issues on the ship.
Android reviewers here might have more insight: https://play.google.com/store/apps/details?id=digiMobile.MainMenu.NCL&hl=en