No. There are no cell towers at sea. All cruise lines offer wifi, the price varies from cruise line to cruise line, as does the speed and quality. CElebtrity offers wifi as a perk. It s not terribly expensive on RCL, Can t remember what I paid, but it wasn t much. Pretty much every port has free wifi, or, in the case of Bermuda, you can buy access pretty cheaply.
If you are using wifi, you won t be using your data. The trick is to put your phone on airplane mode, then turn on wifi calling. If you don t, you will incur international roaming charges and get a really nasty surprise when you get hoe. Another option is to get a portable wifi hot spot. They run about 8$ for a continuous 24 hour block of time. Again, it won t work on the ship but they work great in ports.