AT&T updates Samsung Galaxy S6, S6 edge+ and Note 5 with Wi-Fi Calling, September security patch
All three smartphones will receive an OTA update beginning September 20, but if you don't get it right away don't fret since this is a staged rollout, so it might take a few days to propagate.
The changelog is the same for all three smartphones, so beside the September security patch that you'll be getting, you will also receive Wi-Fi Calling, which enables voice calling and text messaging over Wi-Fi networks.
Also, the update brings Advanced Messaging, which is meant to enable AT&T Advanced Messaging services either you want it or not.
Keep in mind that you will need a Wi-Fi connection in order to capture this update, so it looks like you won't be able to update via AT&T's network. So there you have it, folks, these are all the changes included in this maintenance update
It's also worth noting that in order to receive this software update you must be on a certain baseband version (ending in PD6, PF1, or PG1 for Samsung Galaxy S6; PG1 or PH4 for Samsung Galaxy S6 edge+; PG1 or PH4 for Samsung Galaxy Note 5).
As you probably know by now, to force the update on your smartphone simply head to System / About device / Software update / Check for updates.