exchanging new phone doesnt help. wiping cache doesnt help. full factory reset doesnt help. can happen at any time. when it happens, I can have full 4 bars, people can call me, i can stream music or download file via the 4G, etc. I just cannot make calls.
Many have reported this problem and I'm sure TMO is aware of the problem so let's not keep sending people down the exchange/wipe route.
my theory (after various tests) is that there's a problem in the baseband (radio software) in the android 4.3 update such that when it hands off from one tower to the next, the voice portion is still registered with the old tower while the data is still connected. Our work around is either phone reset or airplane mode, which would force it to reauthenticate with the nearest tower, then all is well.
But we can't go around and resetting our phones 3-5 times a day.