Now when I was on Costa in USVI and PR
, I was on the ship as it was backing out of the docks and talking to my mother, but at that point I was still linked into the land towers. Of course I also keep my phone locked down to NO NONE ZERO roaming. It will only connect to a Sprint tower, so that helps. Same when I was on Carnival in Key West. As we were leaving I was on the phone a lot trying to get ahold of my CU to make sure that a credit card payment happened right. (Thankfully it did, but still).
So again, it all depends on how you configure your phone. Know before you go.