Yes, AT&T has three plans. $30 for 50 talk minutes. $60 for 50 talk minutes and 100 texts. $120 for the 50 minutes, 100 texts, and 100mb of data (maybe that is 300 mb, I forget).
You have to call to get it and it runs for 30 days. It also works in the ports on the local networks. It starts whenever you are on the Cellular At Sea on the ship.
Not cheap but cheaper than not having it and using the same amount of time. It works on Celebrity and Azamara too.