Why do you need wifi calling with a microcell? The whole idea of the microcell is giving you full bars which it does. I use the Note 4 and S4 with it flawlessly. In fact it is my Sister in Laws Iphone that has problems using the microcell.
Beyond that there are many ways to have Wifi calling, I use the MagicJack app but there are other ways to do it.
I feel the Note series are the best phones made. My Note 4 to this day holds up to just about any new phone being made. In fact so good that I decided not to move up to the Note 7 as tempting as it is. It is a little larger than many phones but it doesn't seem so after having it and the screen clarity is superb. There are times the stylus is very handy.
Samsung made some changes in their flavor of Android and it would not connect to the new (black) version of the ATT microcell unless there are no bars on LTE voice. I had to manually go into the manufacturers settings and disable LTE and it would immediately connect to the microcell, then go back and re-enable LTE whenever I left the house. It is a well known problem and there are many posts about it in the ATT forums, Amazon and around the internet. It would connect to the old (orange/white) version of the microcell when I'm at the lake house, but then there is no signal period out there so it wasn't a problem. Also picture messaging would not pass thru the microcell either and I get a lot of photos texted to me from field inspections, before files are closed to be sure that is all we want documented from a scene.
I run my own business and work from home. I need that line and don't want to fool around with call forwarding, magic jacks, land lines etc. I've had that number for 15 years and it's in the emergency contact database for all the Cities I represent and for at least 20 insurance company claim departments as the first contact for my clients.
ATT's answer was to enter that 8 digit code each time and scroll down to enable or disable LTE. I was about ready to leave them, but had other fish to fry, so I just grabbed an iphone6+ and enabled wifi calling. The iphone worked with the microcell ok, but WiFi calling works so well, I just disconnected the microcell and sold it and my Note 4 last week while it was still getting decent prices. No need for the microcell, if my internet goes down I was going to lose service, whether on the microcell or wifi calling and go back to the 1 bar I get inside the house.
I do miss the stylus as it made it easy to notate damage on photos before uploading to my dropbox or box accounts. The Notes camera is many times better than the iphone's and the Note form factor is a lot easier to hold than the iphone 6+ too. Also the Note worked better with the bluetooth in my truck than the iphone. If ATT enables wifi calling on the Note's or Google ever allows them on Project Fi I would switch back to them in a heart beat. As it is I currently have other things to worry about and just want my phone to work when I need it too and not just when I'm outside.
ok my rant is over