Help I am not recieving calls. Is this a Hardware or Network issue?

[MelonSplitter]

I've missed several calls from people saying that I don't answer my phone. I recieve their voicemail but the phone does'nt ring or vibrate, the screen stays completely black.This happens when one of my colleagues calls me from the same carrier as me (SPRINT) with full bars or from any other carrier. I don't use Google Voice so this is not the issue. This happens randomly at home, office or out and about. Has any one else had this happen on their S3?

 

[davidmanvell]

Think this is the phone losing connection to the cell tower. Does this on poor service areas. make sure your phone has latest tower updates and call Sprint for further assistance.

 

[MelonSplitter]

Think this is the phone losing connection to the cell tower. Does this on poor service areas. make sure your phone has latest tower updates and call Sprint for further assistance.

How do I make sure my phone has the latest tower updates?