I have the same issue at work (E4th and Grand). If I toggle airplane mode on/off, my lte works for a breif time, then the spark wheel doesn't move, connection times out, then switches to 3g(it's a good thing i have wifi at work). This has been going on for over a month and i've called sprint 3 times on this issue but nothing seems to get fixed. At first I though it was a devise issue, I have the HTC One M8, but a guy I work with has a S3 and has the same problem at work. Yes, it is very annoying,