And.... I guess no answer. TO VERIZON CUSTOMER SERVIE
I have a 5S that does the same thing, but not all the time- Example: I will text my brother, him me back, I reply- but anything after that I get a Not Delivered error if I reply, but eventually it will go through if I wait a few minutes.
But like right now I have a 4 line text reply that stated not deliverable, but all of the sudden it has been "sending..."
for the last 15 minutes.