its been a bit over a month now since I bought my S4 this happen about 3 times now on the road. When I try to make a call it gives me a error of ( network not registered ) so I restarted it it was fine. I went to the tmobile store were I bought it and they say restart the S4 every other day, is this right ? You spend $600 on a phone and have to reboot it every other day, that sucks. I thought this was the next thing to have. Maybe I should of went to the HTC ONE ?