When I am trying to make a call the call sometimes drops about 10 seconds in or the person can't hear me at all. Text and data are fine. I have had a play with the phone and I can confirm that it only happens with a 4G connection. When I change the phone so that I only allow it a 3G connection it resolves the problem. Also I have tried turning wifi on and off and it makes no difference to the problem I have described above (eg it works in 3G mode and not 4G mode). Also when I make a call and I am on 4G it seems, from what I can tell from the statues bar, that the phone drops the 4G connection and finds a 3 G connection. Anyone else with the same problem? Any thoughts?