Galaxy S6: why are my SMS and MMS dropping or not downloading?

A

AC Question

I've had the S6 on AT&T since April 9 and deactivated my iMessage that day (have since confirmed this twice). Despite this, I continue to have the following issues with messaging:


1) I often see an SMS appear in my notification bar, either while locked or unlocked, but when I open messaging to review and respond, the SMS is gone.


2) While this happens with maybe 20% of SMS, it appears to be far greater than 50% of MMS (that terribly annoying group check box is checked in all of my group texts).

Has anyone else had issues? Messaging is a crucial part of what I require, at a basic level. Is this Samsung, Android, or AT&T? Is there an update coming to correct this?