I used Messenger recently on a Zuiderdam- Fr. Poly trip after the antenna used for WiFi was damaged in Papeete. The cruise home was fought with connectivity problems for all onboard the ship from the bridge down, but I was able to message family in the USA and Portugal without problem. I saw no change to my phone billing. I had been on a ship premium WiFi plan before service konked out and became mostly unusable until 3 days out from San Diego