There are some unanswered questions on this topic such as to how T Mobile's VoLTE mandate will affect MVNOs and Sprint phones, etc. The article says most phones have for years supported VoLTE, but I'm not sure about that. I assume 4G phones without VoLTE capabilities are soon to be obsolete, if that is what is meant.
More info:
"We haven’t shared timing for when we’ll phase out older technologies."
If they're smart, AT&T MVNOs will be preparing a big marketing push specifically pointing out the phones that work on T-Mobile today, won't work on T-Mobile in a few weeks, and will work on the AT&T network.
I know AT&T is a temporary solution -- but 18 months leadtime is a lot better than 2 weeks notice.
If it does affect Sprint phones remaining on the Sprint network, there will be a lot of folks simply out of luck. VoLTE support on Sprint has not been a big thing.
The claim that 'most phones' have for years supported VoLTE is IMHOP, mostly a lie.
- T-Mobile has not specified when the older technologies will be sunset, and certainly not before January 2021. Memo title: "VoLTE Device Compatibility Requirement Begins January 2021".
- The leaked memo only applies to T-Mobile and Metro by T-Mobile. There is no mention of other MVNOs or Sprint.
- "As of August 4, MMobile Experts should begin confirming that BYOD customers have a device that is VoLTE capable before completing an activation." (My take: This directive applies to in-store new activations. If it also applies to online/phone new activations, a BYOD customer with an "ineligible" handset should be able to provide a valid IMEI in order to activate service.)
- Not all phones in your scenario will necessarily work on AT&T (eg; due to technical limitations, locked, etc.)
- Re: "most phones" claim. I googled "overwhelming majority" (this is the language used by T-Mobile). Top result says "70% or more". This may apply only to postpaid/prepaid wholly owned by T-Mobile (excluding Sprint).
Unrelated: I have read anecdotal reports that T-Mobile SIMs may now work in certain Sprint-locked iPhones.
My guess is that you can still make a 3G phone work on T-Mobile until they actually take the 3G network offline. It won't be too different from Verizon, which no longer allows you to activate a phone unless it is compatible with their VoLTE. However, you can still activate on a Verizon VoLTE phone and swap the SIM into a non-VOLTE phone to use 3G CDMA. For example, activate on an iPhone 6 and then put the SIM into an iPhone 5 or 5s
The thing I'm most curious about the decommissioning of 3G on all of the major networks is whether or not you can still use an LTE device that does not have VoLTE (such as the iPhone 5 or 5s) as a data only device after 3G voice goes away. We're going to find out soon enough on Verizon come January.
I also wondered about using phones as a data only device where one could use Google Voice to call via Wi-Fi or VoIP, and I've heard that VoLTE calling is not much different from VoIP or Wi-Fi calling.
"The eventual goal for carriers is to move everyone over to calling on VoIP which stands for Voice over Internet Protocol. Once this happens, features like VoLTE and Wi-Fi Calling will fall into the same category and will allow calling when connected to any secure internet source. This includes standalone 5G and as more efficient 5G networks mature, carriers are going to want customers to stay on that tower as much as possible."
@bingyee When that happens, LTE handsets without VoLTE should "unofficially" work for data only (eg; like swapping phone SIM into hotspot/tablet, etc.) If you have an active Visible SIM (Verizon VoLTE only), you can test this now with an iPhone 5, etc.
@Isamorph I wonder what impact this will have on dialing 911.
ETA:
AT&T: Get ready, 3G is going away in 2022 ("... by February 2022")
Visible won't work on iPhone 5, even for data only. Visible requires that an iPhone run IOS 12 or later. I own several compatible iPhones running IOS 11 but none of them can work on Visible. The iPhone 5 can only get up to IOS 10 and won't work. It's possible that the 5s can support data only on Visible if IOS is fully updated but I can't test that because the only 5s I currently own runs IOS 8 and I'm not going to update it just to see if it will work on Visible
Yes, initial activation of SIM with Visible has to be done on fully compatible handset.
I am pretty sure I successfully used an iPhone 5c on Visible for data only last year. I had to use custom APN generator: iPhone APN Changer
ETA:
APN is 'vsblinternet' if you want to test.
"@Isamorph I wonder what impact this will have on dialing 911"
It appears that VoLTE is likely the gold standard for the ability to call 911, assuming one has reception and is connected to a tower. That said, the 911 emergency landscape is changing: one can now text 911 in some areas, there are some Pixel and Android phones that allow one to connect with emergency services without a data plan, and it may be possible (but who dares test it) to dial 911 successfully from the native dialer on a data only phone with no service provider, since all cell phones are supposed to have that ability without data or a service provider. I do wonder if VoLTE will solve the problem that some neighborhoods have due to poor reception that causes unreliable cell phone reception inside homes, which can put a little damper on 911 calling.
AT&T... 3G goes away in early 2022
Of note to me from that linked article:
"Most smartphones released since 2014 support this technology" (VoLTE)
That is likely true, and follows T-Mobile's similar statement, as long as you don't ask the more relevant question....whether your VoLTE phone will be allowed to use VoLTE on a particular carrier.
AT&T has declined to activate VoLTE on most BYOD phones. Again, I think we're seeing this claim made to minimize an issue that's more prevalent than the carriers want to admit publicly-- that a phone that is VoLTE capable may well not be judged VoLTE capable on any particular carrier.
And the worst part of it, to me, is that real information on what phones will be judged VoLTE capable is still very difficult to come by for most carriers. T-Mobile's VoLTE check tool seems pretty accurate to me, except for a narrow swath of 'we don't know' responses. Verizon's test tool seemed accurate when it was released, but when they delayed 2G shutdown they reverted to giving a green light to non-VoLTE approved phones, instead of grouping results into "acceptable for the time being", and "good when you must have VoLTE'. (I hope they've fixed that problem now-- I haven't checked recently.)
The last thing I'm interested in doing is letting AT&T pressure me into buying a phone now for VoLTE since they're not transparent at all about what BYOD phones they may decide to grant VoLTE status to.
Ways to check if your phone supports VoLTE are linked below. Also, I used the following app from the play store, which appeared to be accurate and informed me correctly that my Xiaomi phone was not VoLTE supported while my other phones were, although this was not apparent from the phones settings.
https://play.google.com/store/apps/details?id=com.voltelte.check (there are several VoLTE checking apps in the play store).
https://www.androidpolice.com/2020/07/24/how-to-find-out-if-your-t-mobile-phone-has-volte-support/
https://www.androidpolice.com/2020/07/24/how-to-find-out-if-your-t-mobile-phone-has-volte-support/
Thanks for the report on actually trying this app: I would have discounted it because it appears to be aimed at verifying VoLTE for carriers in India.
I've had seemingly good results with T-Mobile's own compatibility page, also linked through the AndroidPolice link above:
https://www.t-mobile.com/resources/bring-your-own-phone
This T-Mobile app seems to work pretty well for the more common models, and only needs the first 6 digits of the IMEI (corresponding to manufacturer & model), which might be easier to get from a seller if you're shopping for a new phone.
https://play.google.com/store/apps/details?id=com.tmobile.band12
There are a number of complaints about false results with this app: I've tested about 6 different devices, and only one (older) gave different results than the T-Mobile website check tool. (A result of 'may not be compatible' should be interpreted as 'not compatible with VoLTE': it doesn't seem like they've updated the app to reflect the new anticipated requirement.)
I've tried several different independent websites that have been recommended to check VoLTE and frequency capabilities against multiple carriers. I haven't found one that works correctly across the range of phones I have to test. This seems to be an issue of confusing different versions of a phone, or not actually verifying whether a carrier will accept the phone's VoLTE capability as sufficient for that carrier.
Yes, it not as easy checking phones for VoLTE compatibility as one would image. I tried a few other VoLTE checker apps that weren't to my liking until I tried the linked one that correctly showed my Xiaomi phone was not compatible. I should have added that I uninstalled the app when finished with it, which I think is a good idea with such apps.
One of the problems I encountered is apparently certain phones that do have VoLTE compatibility don't have any info in the settings that show that fact. Oh well, things should become clearer as obsolete day nears. Maybe the MNVOs will weigh in on this matter soon.