I don't think that is the issue. From what I can research the download is fast enough from cellular service for streaming. Also I don't have issues with other streaming apps like NBC, Fox ect.
The buffering, is it from programming on the DVR, VOD content of the channels you're subscribed to? Does it buffer using your phone browser www.dishanywhere.com ? Is your phone and the DishAnywhere app up to date? Have you tried the app on another phone or tablet?