I don't know what the problem is, because I don't have any real difficulty activating the one-handed mode. Naturally the option has to be activated, but you said you already checked that. (I do have to remind myself of this though, since I normally keep so many features off.) I don't think the angle of the swipe is important -- I purposely did it in arcs and angles, ending nowhere near where I started, and it still worked. A very short swipe won't do it, but I seem to be able to activate it with a swipe that goes anywhere from one quarter to almost all the way across the screen. A very slow swipe won't work, but a working swipe doesn't seem to need to be especially fast either. I thought I read that the only trick was that you have to start and stop right at the edge of the screen, so I normally touch the edge of the phone to start, make my swipe, and don't end until I feel the edge again. If nothing is working for you, perhaps there's a problem with your device? If you can get it it to work on someone else's device, an issue with your particular device seems more likely to me. It sounds like you already contacted Sprint, so hopefully they'll be able to provide more help. Good luck.