I agree if you'd have to buy a new phone and you're with Verizon, that it's cheaper to rent their phones.
I'm with TMobile and DH is with AT&T and we both have quad-bands.
TMobile's Internationl Plan is free to add to your plan and you only get charged if you use the phone Internationally.
AT&T charges a monthly fee to add the International Roaming plan to your existing plan.
With TMobile though, I'm planning not to use while onboard the ship, it's $4.99/minute  |