ATT iPhone 5S randomly loses data connection but still reports LTE

I Recently purchased an iPhone 5s for ATT and updated it to iOS 7.1 it works great on wifi but randomly drops data on the carriers network. it wont report any signal loss or show the E or 4G for data connection, just says LTE making me think things are fine. I have tested with my wife's 5s and mine using speedtest.net app and the app on mine will report no connection and hers will get at least 15 megs down. this tells me it isn't a carrier issue. saturday i took it to the apple store and got it swapped out. yesterday I had the problem again. I had to hard-boot the phone to restore the data connection. so far it has worked (about 18 hours) will update this thread as it happens.