From
DCL website -
https://disneycruise.disney.go.com/guest-services/internet-phone-services/
Cell Phone Services
In addition to dedicated locations where you can take advantage of ship-to-shore calling,
Disney Cruise Line features Cellular at Sea phone service—so you can use your own cell phone or wireless PDA just as you would on land. Available from most cell phone carriers including AT&T, Sprint and T-Mobile, this service is currently accessible in staterooms.
Note: Usage rates and international roaming rates vary as you travel. Be sure to contact your cell phone provider to learn these rates before your cruise.
Disney Cruise Line recommends that Guests seeking to avoid the unwanted costs associated with data downloads keep their wireless devices turned off or in airplane mode during their cruise.