On a phone plan all roaming is unlimited including data at least my bill says so. But on a data card plan the roaming limit is 300mb. I had to move my data card over to big red because of the ridiculous 300mb limit. I only use 1gb a month of data but the 300mb roam was a problem some months. So far keeping phones on Sprint and data card on big red, no roaming at all on big red and 4g about 60% of my travels compared to 2% 4g on Sprint. One of my phones was used in a roam area for over a month and used 300 to 400mb roam data per month and almost no Sprint data and I did not hear any complaints from Sprint so just data card plans have a roam problem.