I don't know if this is a GS4 thing or a TMO thing, but every now and then - no rhyme or reason - my data just drops. The 4G is still "on" but the arrows aren't lighting up and there is no connection. Sometimes it will restore itself after a minute or two, sometimes longer. Sometimes it will bounce all the way down to no data, then back up to 4G. Anybody else run in to this? Very frustrating.