I've been having problems with my texts messages failing to send since the July update (received in August) and I knew it was because of the update because it was fine before that. I tried to troubleshoot myself, wiped cache partition, cleared data and cache from messages app, reset network settings, ended up calling T-Mobile support.
They asked me to do all of the above,I told them I already had done those things but I would try again. None of it worked and finally did a factory reset...I really didn't want to do it because I knew if was because of the July update but did it anyway. I still had the same problem. Called Samsung support, I told them about the failed texts, and that I already went through the troubleshooting steps with T-Mobile. T-Mobile said since the phone is still under manufacturer warranty I should contact Samsung. They told me to take to UBreakIFix and have them run diagnostics in it.
UBreakIFix tech runs test,says they're coming up with 8 communication errors,it's not something that a software flash or reset could fix and since I have premium care through Samsung I should make a claim. Now I explained that I just started having the problem since July update,and I really think it's a bug from the update. They said I should file the claim.
Ok, so next day I receive notification for September update, and I update my phone (was on the 18th) and I haven't had a problem with my texts failing to send since! Before this update, I was having issues daily. So it's only been 5 days, BUT the fact that I was having issues everyday and now haven't had them for 5 days since the update is big! If anyone has been having issues, check for the September update and install it!