Hey @michaelh.zwv6tr -
I’ve done WiFi calling on various Carnival, Princess, & Disney cruise ships over the years.
The biggest thing to keep in mind is the cost - the satellite internet provided on the cruise ship is usually expensive (although, in my experience, Carnival is the most reasonable of them all - if I remember correctly, it was around $15 a day. Compared to Disney which charges $90 per GB of data used.)
The next biggest thing is that the network quality is going to vary significantly from hour-to-hour (or even minute-to-minute in some cases). Location, weather, and how many other cruisers are using the network will all impact your ability to make calls & the quality of the calls.
Texting generally worked for me without issues since it requires such a minimal amount of data, but calling has been hit or miss on all the cruises I’ve gone on. You’ll also want to make sure you put your phone in airplane mode & manually turn WiFi back on so that your phone doesn’t constantly search for cell signal.