I have m919 T-Mobile Galaxy s4 but I'm with other carrier (Wind Canada).
I spent yesterday in environment where I didn't had coverage for most of the day, but i haven't gotten it back yet. Sounds really weird as it might be not connected to the fact at all. I have 4G connection active, which means that I have internet, but it keeps 'searching' for service and I can't Call/Text anyone, neither I can receive calls or texts. Instead of the bar at the top showing how good coverage i have it just shows a crossed out circle icon.
I've tried reboots, keeping my phone off for 30mins without battery, taking out sim and putting it back in, changing network modes and resetting APN (all from settings panel).
Have anyone experienced something like that and how do I fix it? It was working perfectly for last couple of months and the phone didn't get any damage yesterday neither.