Yes you can rent DECT phones, last time I checked they were $30 per week.
They work anywhere on the ship.
The beverage package is $6.50 per day for adults and $4.50 for children, that includes a souvenir thermal mug.
I don't know what the water package costs, but I remember it being $$$.
Tap water is safe to drink.....
You can save on the soda package by pre-purchase online, but I don't remember the details..