Wifi Calling on Unlocked Phones?

@GLIMMERMAN76  So correct my rudimentary understandings needed....  is the system is looking for system software in phones, and when it doesn't find the ATT specific configuration, it stops providing HD calling?  Which is why when you flash the ATT software on the unlocked it works, despite the IMEI not being in the system ?

So all ATT has to do is ask the system not to check for their own configuration and we would possible have the same services?  

But they aren't ready to let go of their perceived corner on the cell phone sales corner of the business.  

Here is where their logic completely fails:

-  Did they make a profit on smartphones this year?   With the number of BOGO phones, even as an advertising write off, I don't think they could have.

-  Did the promotions this year increase the customer base?  No, If I read correctly, ATT was the biggest loser this year.  Maybe because the promos were poorly run.

-  Are they losing customers with BYOD phones to T-Mo and Verizon?  Yes.   And this is going to increase because more and more customers are buying unlocked.  All 5 Best Buy locations with 30 minutes of me have the unlocked phones in an impressive display in the center of the store.  I'm sure these are pure profit and no fussy paperwork for BB.  

Does this mean that it may be possible to use the carrier autoloader to push the "app" if it is part of the loaded system?  For example, could I load the AT&T image for the Priv (STV100-1) on the unlocked carrier Priv (STV100-1), i.e. same hardware. http://us.blackberry.com/support/smartphones/Android-OS-Reload.html

Cool pointer @GLIMMERMAN76.  I figured it was something along these lines.

Because of the signed cert, per the one on the SIM, an app, or "build your own" is going to be almost impossible, unfortunately.

@GeekBoy I don't think this is the IMEI, it's just got the correct code (or not), and you can't very well fake it, because even if you tweak it, it'll figure out you don't have the cert (the same way it fails after a short time if the SIM is brought over from a working device).

What's interesting, if you look at the "they're avoid problem devices" issue, I don't see this, at least not much, on the T-Mobile forums (I used to spend some time up there, before I had them, while I was with them for a few weeks, and off/on occasionally since).  What you do see is a lot of smug "yeah, we don't have those issues".  I agree 100% that not all OEM implementations are great, and some are probably a bit sketchy, but the user can "choose" this at least.

Yeah, I'm with @lizdance40, it's hard for me to understand the "win", the way things are right now, it seems like the time for playing chicken is probably a bit late, but who am I to say, maybe there are numbers we're not seeing, or a trend, or who knows.  More BYOD is just going to generate more ill-will towards this though, it seems eventually like a losing game, any way you slice it, unless trends change again (I sort of doubt it, I think people are a bit tired of being "held hostage" for updates, plus bloatware, etc).

Oh yeah, my 6P is an "unknown device" too, as is an HTC M8 that I "de-branded" quite some time ago, even though it was originally an AT&T device.  Re-registering it doesn't change things, I suspect I'd have to find their firmware to go back to registered, but since it's a Win phone, it's not as if it would get "extra" features anyway...

@pgrey  Again, my totally unsubstantiated theory is that ATT preorders phone's months possibly up to a year ahead of time.  So maybe they ordered too many phones, then saw the sales tank last quarter of 2015.  So the solution they cobbled together with so many phones coming in, was to BOGO and bring in new lines.  

They don't want to have too few phones, but haven't adjusted to the new demand (or lack of). 

I have been reading up on AT&T HD voice/Enhanced LTE for unlcoked devices more and more in the past several months...I suspect there is more behind the scenes here than ATT just needing to flip the switch to open the flood gates or having enough folks knocking on the VPs doors to turn heads.  

I can give my two cents being primarily a Windows 10 Mobile user now, but also using iOS and Android over many years...

For Windows mobile is not as simple as editing a single file on an unlocked device like Android's build.prop file.  The HD voice/VoLTE code is baked into the ATT Windows Variant ROM and provisions the code/settings to the modem partions and maybe updates other items also.  Then when the OS sets up it updates the necessary software and regstistry settings on initial boot or after a reset during which time the sim card is available.  There are ways to using an unlocked Windows Phone with HD Voice/VoLTE sevices on ATT, but you have to know what you are getting into, and need to pick the right device.  There is more history in the way of iOS but it seems the way they are proviosioned on the backend is obviously different than other devices, in general the OS is built different and I also assume Apples carrier involvement/proprietary ways helped with this also.  How else are all unlocked iphones 6 and up able to use GSM VOWiFi/VoLTE/HD Voice for T-MO ATT and VZW.

Obviously AT&T have the upper hand.  Though not entirely, it shows they have control over who is using what on their network, and that does bring a secure network to front. Thought it would be nice to see them change their ways and make way for unlocked devices like the trend is lately, but AT&T may have an entirely different plan to go about it.  The easiest way though to voice what we need, might be if enough folks wanted would get up and move their unlocked device to T-Mobile.  I honestly considered this months ago...but I believe it will only take time before AT&T follows the trend being set by VZ and T-MO.