HD Voice / VoLTE on Unbranded (Non-AT&T) Devices

as of right now no it wont work it needs a firmware patch to enable hd voice(and as you stated att does not support the z3 lines).  The other cleavet is the other person has to have an hd voice phone and be in an hd voice area for the call to be in HD.

no as of right now just like verizon att is doing it there way.

and by the way your phone is missing band 5,17 LTE which are ATT bands according to your post.  

EDIT:   but the white paper says its has the right ones so your good

D5803 UMTS HSPA+ 850 (Band V), 900 (Band VIII), 1700 (Band IV),
1900 (Band II), 2100 (Band I) MHz
GSM GPRS/EDGE 850, 900, 1800, 1900 MHz
LTE (Bands 1, 2, 3, 4, 5, 7, 8, 13, 17, 20)

http://www.att.com/shop/wireless/services/hd-voice.html#fbid=91PDk92osTc

and here are the limited devices that work with it

http://www.att.com/shop/wireless/devices/smartphones.html?taxoFeatures=HD-Voice

Hello Glimmerman,

Thank you for your response.  For clarification, my device is a Band 1/2/3/4/5/7/8/13/17/20 phone.  It is the version built specifically for US and Canadian customers.

The list you provided from AT&T's website is very helpful for prospective AT&T customers or those existing custromers looking to buy a new phone in-house.

However, since it is very unlikely AT&T will add Sony devices to their linup in this generation (it has been a couple years) than I can be relatively certain AT&T will never add my device to this list.

My question is, provided A. My radio hardware already fully supports AT&T LTE, and B. My manufacturor already includes VoLTE support out-of-box, will AT&T's "HD Voice" service work?

I am not looking for any promises. I understand it is never the carrier's job to test and certify outside devices.  I would simply like to know if AT&T is perhaps using different protocols for their VoLTE compared with other carriers.  Is AT&T's VoLTE HD Voice is some way different from others?  Thank you.