Admittedly i don't use 3G (or really 4G) at all anymore for data because LTE is pretty much everywhere that i find myself...i was, however, in a building the other day that caused my iPhone to cut down to 4G, and when i tried to check an email that had pictures included, it was quite slow. I attribute it to the fact that LTE speeds on this device are blazingly fast though, and not to a "problem" honestly. You may very well have an issue with your device, but to me, the difference between LTE and 3G/4G is very close to that of dial up vs. broadband, and that can be a bit shocking initially.