[AT&T Samsung Galaxy S6] sentinel_cm:
I'll throw my hat in the ring on this one, because it has been driving me crazy for 6+ weeks now....

I called the updated number on the first post in this thread and gave them the case # and asked to be added because I was having the same issues with my S6 Active. First she had me hang up with her and turned off the "Enhanced 4G LTE Services", and reboot my phone. She called back and sent me a test picture, which came through OK via text. Then she had me try to send one which just tried and tried but did not go. Then she said she made another change to my phones account and had me hang up and reboot again. Then send another test picture to someone, which they got, although it could have been just because I rebooted my phone too, oh and she had me turn my wifi off, and also cycle standard data off and on too. She said she made 2 "major" changes to my account and to test it out for 24 to 48 hours and call them back. Not sure if I should leave my "Enhanced 4G LTE Services" off or not, but I'll try and see what happens. (Settings>Connections>Mobile Networks>Modile Data>Enhanced 4G LTE Services)

On to more of my testing.... after we hung up, tried sending a picture at 11:12am, by 11:16am it was still not sending, so I bounced Airplane mode (turned it on and off)... BOOM.... it went right through... I have had this experience before, so I don't thing the "major change" they made to my account had any effect. This was done with the "Enhanced 4G LTE Services" still off.

So now to try turning "Enhanced 4G LTE Services" back on., with another reboot for good measure. I picked a much smaller picture than my phone is normally set to take and it sent INSTANTLY... then I noticed it had dropped me off the Micro cell too and sent over normal LTE . And it didn't look like it was ever going to connect back to the micro cell, so I tried another pic ("normal" sized)... as I hit send it connected back to the micro cell and seemed to try and try but never actually send.... I bounced airplane mode again. It sent, but over LTE before the Micro Cell could connect (I do get 1 or 2 bars without the MC, but not reliably), which take a min or two after airplane mode.

Ok, once more with Enhanced 4G LTE Services OFF and a reboot, waiting to fully be on my MC again... Wish I knew why it takes so long to re-connect to the MC too, this time that reconnect to the MC took almost 5 mins... tried again and waited 3 mins and the normal sized pic sent, but another didn't go after 8 mins, so I bounced airplane mode, but it wouldn't go. It doesn't seem to matter if the recipient is on ATT or another network. I tried all of this again and couldn't get a pic to send at all..... SIGH!!!

My conclusion so far is that turning OFF the "Enhanced 4G LTE Services" (and whatever changes they made) seems to prevent me Galaxy S6 Active disconnecting from my MicroCell. But it doesn't really improve my ability to send pictures (MMS).

On a side note, the advanced team did not appreciate me calling them directly however they did spend over 30 mins with me making changes on their end and trying to help, they were very nice, once I got "the speech" about calling them directly without calling level on support first. They did not add me to the existing case # or give me my own yet. I will call them back tomorrow and go forward, but I will be at work and it will be difficult to test.

Chris