Never heard of your phone type but all quadband and hopefully triband phones will work on the ship even when at sea but not cheap. I use texting when at sea and the odd call when ashore, unless a real emergency. I always put £70 credit in my phone to cover but so far have never spent more than £10, but it is there and of course you could top it up if necessary. Everytime I switched the phone on in the morning at a new island I got a nice welcome message from their mobile phone provider. On an open website never tell an exact date when you will be away from home, as you never know who is reading these messages.
Think you would need to check with Sprint your mobile Service provider. This is a UK site so we wontbe familiar with the US Sprint Network.