I have the same problem, Samsung S5, receive msgs but can't reply or initiate a text. Done hard reset twice, clear cache, used third party app, stock app and Verizon app, etc. I have an open technical ticket with Verizon right now. They are telling me it is not my S5, that it's a network conflict between Samsung S5 and their network. It seems many folks are having the same problem.
Sent from my SM-G900V using Tapatalk