🇺🇸 XZ1 Does Not Support Wi-Fi Calling/VoLTE on T-Mobile US

[romanempire]

TL;DR: Dear support, could you please register a complaint about Wi-Fi calling (and VoLTE) not being supported with T-Mobile in US to aid in prioritization?

Since the price on US Amazon dropped another $50 for XPERIA XZ1 (down to $600 from $700 initially, then $650), I have hard time justifying keeping the device, which does not have phone capabilities for those 6 hours daily when I am in a location full of Wi-Fi but poor T-Mobile coverage.

So I got in chat with both T-Mobile US and Sony to figure out who to blame for XPERIA XZ1 not being able to use VoLTE and Wi-Fi calling.

Sony suggests that's carrier:

Contact your network operator to verify what is valid for your Xperia™ device model.
you have to use a VoLTE-supported phone or tablet.

• Your operator and subscription (incl. SIM card) must support VoLTE for the device model you're using.
• Depending on operator, your phone or tablet must sometimes be operator-branded and/or use operator-customised system software.
• Your phone or tablet must be in range of a LTE/4G network.

Well, the phone is quite similar to XZ1 Compact, and the bigger and more expensive version lacks configuration that would run a customized modem software, which is already present on the filesystem.

So I contacted T-Mobile and got a response:

I'm sorry Sony directed you to us about their firmware, we've carried the Z1s and Z and Z3, so *technically* Sony has our Wi-Fi Calling firmware in their hands but they're probably restricted from using it. The most common cause of a lack of VoLTE on any third-party phone is a lack of vetting of their equipment on our network, that's something that happens behind the scenes between our back office and a phone manufacturer's.

 Since part of switching to a newer phone was to get a better coverage, be it a 700 MHz or Wi-Fi calling indoors, there is now one less reason to keep the phone. US launch of XPERIA XZ1 seems to have been rushed.

For people in the rest of the world where unlocked phones compete properly, congratulations! If you have VoLTE and Wi-Fi calling working on your carrier, I envy you :).

[ezy2ezy]

Is it Sony's fault or the operator ?

In the UK the voice over wifi is a marketing tool that the carriers keep for handsets they sell and not the same handset bought outside of their own shop  (i.e. it has to have the carrier firmware) 

so EE, Vodafone & O2 sell the XZ1 as they did the Z5 with their own firmware with wifi enabled... but buy a phone from another source and wifi calling is not an option.   (O2 have a second wifi calling service that is provided via an app that can be downloaded to give something similar though). 

Apple phones through design do not allow such carrier firmware restrictions and some Samsungs and other handsets have also managed to avoid EE (for sure) firmware only provisions...   

But if it is the carrier that is restricting it to their own supplied handsets then Sony may not have the right to enable the option (let alone the carrier to then recognise the handset being turned on for the service) 

Wifi calling is still being used as a "differentiator" in sales channel offerings 

[romanempire]

Given that XPERIA XZ1 Compact loads the corresponding modem customizations for TMO US, it appears that there was some communication between Sony and T-Mobile on this feature. T-Mobile also does not brand Google Pixels, but they have VoLTE and Wi-Fi calling support. So while I understand there is no way we find out about why that happened, on the software side there is no technical reason to disable these features.

[Uliwooly]

@romanempire

That's on the operator/network/carrier to enable such features. 

[romanempire]

True, but how can Sony justify enabling VoLTE on the cheaper and smaller device, but not on the bigger device released at the same time with identical CPU/Modem configuration? Not asking as a rhetorical question, just can't understand this.

[romanempire]

Update: MSM8998 modem used in all XZ1s supports:

Multi SIM

• LTE Dual SIM Dual Standby (DSDS)

Next-generation Calling Services

• VoLTE with SRVCC to 3G and 2G

I may have found the reason. Will create a new topic, since it looks like either we got the wrong model, or the difference of implementation for Single-SIM XZ1 Compact/Dual SIM XZ1 is the reason for VoLTE/Wi-Fi calling to be unavailable.

PS. romanempire=eniweb, that's what you get when you click through the registration process and pick birthday at random.

[MarkV58]

Found this review of the Experia XZ1 Compact on Amazon's site.  User states that they bought unlocked phone and went to T-Mobile for a compatible nano sim card.  voLTE and WiFi calling were enabled - no issues.  Also read an article that stated Sony certified the XZ1 Compact with T-Mobile.

So the question for Sony is why did they not certify the XZ1 with T-Mobile?  Basically, same phone from same series.  It is true you can get LTE to work with these phones XZ1 and XZ premium, but on AT&T you do not get voLTE or WiFi calling.  

I appears that that it is up to Sony to code the capabilty into the firmware on these phones to gain access to these premium LTE features on specific US carriers.  Sony, I'd like to buy your phone XZ1 or XZ premium, but I'm on AT&T and don't want to deal with all the BS I've read I must go through in order to get LTE to work.  Most importantly, if I'm going to spend the money on these phones I want all features to work - voLTE, wiFi calling...

Sony, if you want to sell phones in the US make it easy for consumers to access the LTE features.  

https://www.amazon.com/gp/product/B074P5FMGC/ref=s9u_simh_gw_i1?ie=UTF8&fpl=fresh&pd_rd_i=B074P5FMGC...

[romanempire]

Support Case *personal info hidden*

Last update from CS rep Valentina Rincon:

I'm glad to confirm for you that the XZ1 indeed is built with VoWIFI and VoLTEtechnologies, however, this feature to be used, has to be supported by your network provider, not only through activating the feature but also with a compatible SIM card provided by them.

Before that, update from Nestor Salinas:

In order to solve your question about VoWifi or WiFi Calling service, here I send some information related with.

VoWifi (Voice over Wi-Fi) is a telephony service provided by your network operator. It means that your network operator provides a voice call service using Wi-Fi®.

To use VoWifi or Wi-Fi Calling, your device needs operator-customised software and your subscription (incl. SIM card) must support Wi-Fi Calling for the device model you're using. To inquire if your subscription and SIM card support VoWifi/Wi-Fi Calling, contact your mobile network operator.

To make a VoWifi call you need the recipient’s phone number.

The following Xperia™ devices support VoWifi:

• Xperia™ L1
• Xperia™ X/X Dual SIM
• Xperia™ X Compact
• Xperia™ X Performance/X Performance Dual SIM
• Xperia™ XA1
• Xperia™ XA1 Ultra
• Xperia™ XA1 Plus
• Xperia™ XZ Premium/XZ Premium Dual SIM
• Xperia™ XZ/XZ Dual SIM
• Xperia™ XZs/XZs Dual SIM
• Xperia™ XZ1
• Xperia™ XZ1 Compact
• Xperia™ Z5/Z5 Dual
• Xperia™ Z5 Compact
• Xperia™ Z5 Premium/Z5 Premium

Note!: Your network operator decides if VoWifi/Wi-Fi Calling is enabled or not in your device.

I hope all this information will be clear and helpful for you to get all those services in your Xperia.

Asked to clarify whether XZ1 refers to G8342 (Dual SIM, US) or G8341 (Single SIM, Europe). At this point I understand that VoLTE and Wi-Fi calling will NOT work for any US carrier.

[romanempire]

I received two conflicting messages from Support, the first one via email:

Regarding your the request about the devices with VoLTE and Wi-Fi calling feature, specifically Xperia XZ1, you can find both models available in US: 

• Xperia XZ1 (G3121/G3123/G3125)
• Xperia XZ1 Dual SIM (G8342)

The G3121/G3123/G3125 models are XPERIA XA1, not XZ1. Then, via Twitter:

@SonyXperiaUS The US devices are single SIM

Asked to clarify again, since that's not what gets sold on Amazon and in Best Buy (where listing mentions both G8341 and G8342)

XperiCheck does not show US firmware for G8341, so I am inclined to say that there is a miscommunication within Sony about which model they were bringing to US. If that was G8341, then there may have been a higher chance of having T-Mobile firmware running.

[romanempire · Accepted solution]

Today I got XZ1 Compact and tested Wi-Fi calling on T-Mobile. It is present and it works. I have yet to test VoLTE over Band 12, but I'd recommend anybody considering XZ1 AND T-Mobile to look at XZ1 Compact instead.

Stillwant to figure out why there is so much uncertainty around XZ1, single SIM, VoLTE and VoWiFi.